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Softpanorama
(slightly skeptical)
Open Source Software Educational Society |
May the
source be with you,
but remember the KISS principle ;-)
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Virtual Machines
as a Special Class of Operating Systems
Virtualization was pioneered by IBM with is ground breaking VM/CMS. Also
IBM mainframe hardware was the first virtualization friendly hardware.
As Intel CPU got traction everything was that were invented for other CPUs was
reinvented for Intel. In 1998 VMware built VMware
Workstation, which ran on a PC despite the fact that Intel CPu did not directly
supported virtualization at this time.
The first mass deployment was not servers but "legacy desktop applications".
Enterprises needed a way to run old applications when moving to new PCs and VMware
provided a very good path. This was one can run Windows 9X in a virtual machine
while running XP as the main desktop.
Later this was also used to run linux on the same Pc as Windows. This was very
convenient for various demo and such configuration became holy grail of all types
of consultants.
The latest Holy Grail of large corporate IT is server consolidation. In
an attempt to lower the costs of IT infrastructure many companies are looking to
achieve this via server virtualization. Of course you cannot defy gravity with virtualization:
you still a single challenge to RAM and with several OS running concurrently it
can became a bottleneck. Still the idea is to consolidate small and not very loaded
servers into fewer and larger as well as more heavily-loaded physical servers was
a sound one. Typically large enterprise runs dozens of servers that just circulate
air, sometime in a very exact sense of this word. But here is it very important
to avoid excessive zeal. If overdone this can bring up a whole new set of complications,
however, as there is no free lunch. But in moderation this new trend that
lead to called conversion of "low load" servers into set of
Virtual Machines. this is a win-win situation. It
is quite beneficial for environment and for the enterprize as it opens some additional,
non-foreseen avenues of savings. Please note that the price of servers grow
very fast beyond midrange servers and, say, an Intel server that cost $35 will never
be able to replace 7 reasonably loaded low end servers. But if they are not loaded
or systematically loaded below 0.1 at can be a very good fit.
Also if done intelligently virtualization can probably squeeze the number of
the low end servers in a typical datacenter 30-50% and that also lead to some modest
maintenance cost savings as well as electricity and air-conditioning related savings
(low end servers as very wasteful as for electricity and add considerable to air-conditioning
costs as their power supplies are very inefficient).
Saving on hardware is more questionable as low level servers represent the most
competitive segment of server market with profit margins squeezed to minimum; the
margins are generally much larger of mid-range and high end servers. In other
words margins on midrange servers and high-end servers work against virtualization.
At the same time the heavy reliance on virtualized servers for production applications,
as well as the task of managing and provisioning them, are fairly new areas in the
"new brave" virtualized IT world and both need special software solutions. That
increases the importance of Tivoli and
other ESM applications. Virtualization has changed configuration management, capacity
management, provisioning, patch management, back-ups, and software licensing. It
is inherently favorable toward open source software and OS solutions. It also opens
a lot of new possibilities in saving time on administration, electricity savings
as well as makes some impressive feats like dynamic migration of a virtual instance
from one (more loaded) physical server to another (less loaded) possible.
We can distinguish the following five different types of virtualization:
This is hardware domain-based virtualization that is used only on high-end servers.
Domain can, essentially, be called "blades with common memory and I/O devices".
Those "blades on steroids" are probably the closest thing on getting more power
from a singe server without related sacrifices in CPU, memory access and I/O speed,
sacrifices that are typical for all other virtualization solutions. Of course there
is no free lunch and you need to pay for such luxury. Sun is the most prominent
vendor of such servers (mainframe class servers like E15K, etc are all hardware
domain-based).
Access to memory of other domains is slower then to local memory so those systems
are closer to NUMA.
By heavy-weight virtualization we will understand full hardware
virtualization.
IBM calls it LPARs and is currently the king of the hill in this area as it pioneered
this class of VM machines in late 60 with the release of famous VM/CMS.
Until recently Power5 based server with AIX were the most battle-tested and reliable
virtualized environments based on heavy-weight virtualization concept.
Still the most popular implementation of this concept currently is VMware and
recently it was greatly helped by Intel and ADM who incorporated virtualization
extensions in their CPUs. VMware can run Linux (Red Hat and Suse), Solaris
and Windows virtual instances on one physical server and as such is the most versatile
solution on this category although IBM Power5 servers still enjoy the advantages
of hardware designed with the virtualization in mind.
But with Intel quad CPUs available you can have pretty impressive CPU power on
a single Intel server and that makes VMware more important as rising tide of Intel
server power (as well as AMD competitive efforts to match Intel after its introduction
of 5xxx series of CPUs -- Duo and Quattro) lifts all boats.
On newer Intel and AMD CPUs Xen also can run unmodified OS instances making it
another heavy-weight virtualization platform.
Sun calls heavy-weight virtual partitions "logical
domains"(LDOM) and until recently preferred hardware-base domains to logical
domains. But this stance is changing with the introduction of LDOMs on Sun's T1000
and T2000 Sun Fire servers. The first is low end server and as such is questionable
platform for heavy-weight virtualization, the second is actually something in between
low end and middle-weight server and can run at least two or may be three virtual
partitions with substantial simultaneous loads. I am not sure what is the speed
of memory for T2000 but I doubt that it is 1.33GHz. It is probably lower so in this
area T2000 is inferior to newer Intel 5xxxx based servers.
Customers that use Solaris 10 11/06 can turn to new hardware being shipped in
January or a firmware update on older boxes in order to get LDOMs working on their
UltraSPARC T1-based servers. Sun will support up to 32 operating systems per server
with the virtualization technology. About differences with LPARs see
Rolf M Dietze blog. Among
other things he came to the following conclusions:
Sun’s LDoms supply a virtual terminal server,
so you have consoles for the partitions, but I guess this comes out of the UNIX
history: You don’t like flying without any sight or instruments at high speed
through caves, do you? So you need a console for a partition! T2000 with LDoms
seems to support this, at IBM you need to buy an HMC (Linux-PC with HMC-software).
With crossbow virtual network comes to Solaris.
LDoms seem to give all advantages of logical partitioning as IBMs have, but
hopefully a bit faster and clearly less power consumption.
Sun offers a far more open licensing of course
and: You do not need a Windows-PC to administer the machine (iSeries OS/400
is administered from such a thing).
A T2000 is fast and has up to 8 cores (32 thread-CPUs)
16GBRam and has a good price and those that do not really need the pure power
and are more interested in partitioning.
The Solaris zones have some restrictions aka
no NFS/server in zones etc. That is where LDoms come in. That’s why I want to
actually compare LDoms and LPARs.
It looks like it becomes cold out there for IBM
boxes….
CPU vendors now are paying huge attention to virtualization. All new CPUs are
usually "virtualization-friendly" and contain instructions and hardware capabilities
that make heavy-weight virtualization more efficient. Intel 5xxx series (Duo and
Quattro CPUs) is an example of this class of CPUs among Intel-compatible CPUs.
IBM P5 and Sun UltraSparc T1 are examples among RISK CPUs.
The main advantage of heavy-weight virtualization is almost complete isolation
of instances. You cannot achieve this with any other type of virtualization
and here only blades can compete.
Disadvantages are connected with the fact that both CPUs, memory and I/O are
shared and you will never get the same speed on high workloads as in case of several
standalone servers each with corresponding fraction of CPUs and memory and the same
set of applications. Especially problematic is sharing of memory as it might well
become a bottleneck before CPU. Each virtual instance of OS loads pages independently
of the other and compete for memory bandwidth. So if, for example, two virtual
instances are simultaneously active and for example are loading modules or data
from the disk each can enjoy probably only 2/3 of the memory bandwidth (accesses
to memory are randomly spread in time so sum should probably be greater then 100%)
in comparison with a standalone system. In other words you lose approximately
1/3 of memory bandwidth by jumping into virtualization bandwagon. That's why
heavy-weight virtualization behaves bad on memory intensive applications. Users
of IBM Power5 servers and AIX 5.3 (probably are the best and the most widely used
commercial heavyweight virtualization platform) know that all too well.
As memory channel is shared between all virtual instances heavy-weight virtualization
is best suited for Web and e-commerce workloads.
That probably means that other things equal you should strive for the fastest
memory and the best designed memory bus (Opteron has better memory bus then Intel
CPUs). That's probably why new 5xxx series of CPU that support 1.3Ghz memory significantly
improves the performance of the VMware (see Dell paper about the improvements achieved).
Both memory speed and CPU power can became bottlenecks as they are shared between
all active virtual instances of OS. The presence of a full non-modified version
of an OS for each partition introduces significant drag on resources (both memory
and CPU-wise). I/O load can be diminished by using a separate controller for
OS partitions and multiple controllers on the server. Still in some deep sense heavy-weight
partitioning is inefficient and will always waist significant part of server resources.
In IBM Power-based server world "binary" deployments when a single server host two
application in two different LPARs are common pretty popular and behave reasonably
well. Taken to the extreme this approach guarantee 50% reduction of all physical
servers. Larger number of applications on a single server are possible, but more
tricky: such virtual server need careful planning as it faces memory bottleneck
and CPU power bottleneck, especially painful if "rush hours" are the same
for both applications. We need to understand that a larger server with two
CPU and 8G of memory split equally between two partitions will always be less efficient
then two several servers with one CPU and 4G of memory if speed of memory and speed
of CPU are equal. As an alterative to heavy-weight partitioning see blade servers
discussion below.
This approach is important for running legacy applications like application for
SunOS 4.x as well as few linux applications that makes sense to run of Linux instead
of Solaris but that need to run on the same server.
Para-virtualization is a variant of native virtualization, where the VM
(hypervisor) emulates only part of hardware and provides a special API requiring
OS modifications. The most popular representative of this approach is
Xen with
AIX as a distant second:
With Xen virtualization, a thin software layer known as the Xen hypervisor
is inserted between the server’s hardware and the operating system. This provides
an abstraction layer that allows each physical server to run one or more “virtual
servers,” effectively decoupling the operating system and its applications from
the underlying physical server.
Therefore only specially modified for Xen versions on OS can run in virtual mode.
Work on Xen has been supported by UK EPSRC grant GR/S01894, Intel Research, HP Labs
and Microsoft Research (Yes, despite naive Linux zealots wining Microsoft did contributed
code to Linux ;-). Other things equal it provides higher speed and less overhead
then native virtualization.
NetBSD was
the first to implement Xen. Currently the key platform for Xen is linux with
Novell supporting it in production version of Suse. Red Hat does not support it
in RHEL 4 but is expected to support in RHEL 5 somewhere in 2007. Sun Solaris 10
for x86 also have Xen support (currently in beta with production version in early
2007).
Xen is now sold commercially by
IBM; Sun will have Xen compatible version of Solaris in mid 2007. SPARC has separate
implementation that will be released in late 2007 and two implementations re expected
to merge in the future).
The main advantage of Xen is that it supports live relocation capability. It
is also more cost effective solution the VMware that is definitely overpriced.
The main problem is that para-virtualization requires OS kernel modification to be aware of the environment it is running and pass control to
hypervisor in case of executing all privileged instructions. Therefore it
is not suitable for running legacy OSes and for running Microsoft Windows
(although Xen can run it in newer 51xx CPU series)
Para-virtualization improves speed in comparison with heavy-weight virtualization
(much less context switching),
but does little beyond that. It is unclear how much faster is para-virtualized instance
of OS in comparison with heavy-weight virtualization on "virtualization-friendly"
CPUs. Xen page claims that:
Xen offers near-native performance for virtual servers with up to 10 times
less overhead than proprietary offerings, and benchmarked overhead of well under
5% in most cases compared to 35% or higher overhead rates for other virtualization
technologies.
It's unclear was this difference measured of old Intel CPU or new 5xxx series
that support virtualization extensions. I suspect the difference on newer CPUs
should be smaller.
I would like to stress it again that the level of modification OS is very basic
and important idea of factoring out common functions like virtual memory management
that was implemented in classic VM/CMS is not utilized.
Therefore all the redundant processing typical for heavy-weight virtualization is
present in para-virtualization environment.
Note: Xen 3.0 and
above support both para-virtualization and full (heavy-weight) virtualization to
leverage the built-in hardware support built into the Intel-VT-x and AMD Pacifica
processors. According to XenSource
Products - Xen 3.0 page:
With the 3.0 release, Xen extends its feature leadership with functionality
required to virtualize the servers found in today’s enterprise data centers.
New features include:
- Support for up to 32-way SMP guest
- Intel® VT-x and AMD Pacifica hardware virtualization support
- PAE support for 32 bit servers with over 4 GB memory
- x86/64 support for both AMD64 and EM64T
This type of virtualization was pioneered in Free BCD (jails) and was further
developed by Sun and introduced in Solaris 10 as concept of
Zones. There are various experimental add-ons of this type for Linux but
none got any prominence.
In Solaris 10 11/06, the next build of the operating system that will be released
at the end of November, admins will be able to clone a Zone as well as relocate
it to another box, through a feature called Attach/Detach.
Also now it is possible to run Linux applications in zones on X86 servers
(branded zones). The key advantage is that you have a single instance of OS
so the price that you paid in case of heavy-weight virtualization is waived. That
means that light-weight virtualization is the most efficient resources-wise. It
also has great security value. Memory can become a bottleneck here as all memory
accesses are channeled via a single controller.
IBM's "lightweight" product would be "Workload
manager" for AIX which is an older (2001 ???)and less elegant technology then
BSD Jails and Solaris zones:
Current UNIX offerings for partitioning and workload management have clear architectural
differences. Partitioning creates isolation between multiple applications running
on a single server, hosting multiple instances of the operating system. Workload
management supplies effective management of multiple, diverse workloads to efficiently
share a single copy of the operating system and a common pool of resources
IBM lightweight virtualization operates under a different paradigm with the most
close thing to zone being a "class". The system administrator (root) can delegate
the administration of the subclasses of each superclass to a superclass administrator
(a non-root user). Unlike zones classes can be nested:
The central concept of WLM is the class. A class
is a collection of processes (jobs) that has a single set of resource limits
applied to it. WLM assigns processes to the various classes and
controls the allocation of system resources among the different classes.
For this purpose, WLM uses class assignment rules
and per-class resource shares and limits set by the system administrator.
T he resource entitlements and limits are enforced at the class level. This
is a way of defining classes of service and regulating the resource utilization
of each class of applications to prevent applications
with very different resource utilization patterns from interfering with each
other when they are sharing a single server.
Blade servers are an increasingly important part of the enterprise datacenters,
with consistent double-digit growth easily outpacing the overall server market.
IDC estimated that 500,000 blade servers were sold in 2005, or 7% of the total market,
with customers spending $2.1 billion.
While blades are not virtualization in pure technical sense, the rack with blades
(bladesystem) possesses some additional management capabilities that are not present
in stand-alone U1 servers and in modern versions usually have shared I/O channel
to NAS. They can be viewed as "hardware factorization" approach to server
construction which is not that different from virtualization. The first shot
in this direction is the new generation of bladesystems like IBM BladeCenter H system
has offered I/O virtualization since February, 2006 and HP BladeSystem c-Class.
The latter offers better server management, virtualization and saves up to 30% power
in comparison with rack mounted 1U servers with identical CPU and memory configurations.
Sun also offers blades but it is a minor player in this area. It offers
pretty interesting and innovative
Sun Blade 8000 Modular System
which target higher end that usual blade servers. Here is how Cnet
described the key idea behind the server if the article
Sun defends big blade server 'Size matters':
Sun co-founder
Andy Bechtolsheim, the company's top x86 server designer and a respected
computer engineer, shed light on his technical reasoning for the move.
"It's not that our blade is too large. It's that the others are too small,"
he said.
Today's dual-core processors will be followed by models with four, eight
and 16 cores, Bechtolsheim said. "There are two megatrends in servers: miniaturization
and multicore--quad-core, octo-core, hexadeci-core. You definitely want bigger
blades with more memory and more input-output."
When blade server leaders IBM and HP introduced their second-generation blade
chassis earlier this year, both chose larger products. IBM's grew 3.5 inches
taller, while HP's grew 7 inches taller. But opinions vary on whether Bechtolsheim's
prediction of even larger systems will come true.
"You're going to have bigger chassis," said IDC analyst John Humphries, because
blade server applications are expanding from lower-end tasks such as e-mail
to higher-end tasks such as databases. On the more cautious side is Illuminata
analyst Gordon Haff, who said that with IBM and HP just at the beginning of
a new blade chassis generation, "I don't see them rushing to add additional
chassis any time soon."
Business reasons as well as technology reasons led Sun to re-enter the blade
server arena with big blades rather than more conventional smaller models that
sell in higher volumes, said the Santa Clara, Calif.-based company's top server
executive, John Fowler. "We believe there is a market for a high-end capabilities.
And sometimes you go to where the competition isn't," Fowler said.
As a result of such factorization more and more functions move to the blade enclosure.
As a result power consumption improves dramatically as blades typically use low
power dissipating CPUs and all blades typically share the same power supply that
in case of full or nearly full rack permits power supply to work with much greater
power efficiency (twice of more efficient then on a typical server). That cuts air
conditioning costs too. also newer blades monitor air flow and adjust fans accordingly.
As a result energy bill can be half of the same amount of U1 servers.
Blades generally solves the problem of lack of CPU power typical for most types
of virtualization except domain-based, and with the current price of memory it solves
the memory latency problem. Think about them are predefined partitions with fixed
amount of CPU and memory. Dynamic swap of images between blades is possible.
Some I/O can be local and with high speed solid drives very reliable and fast. That
permits offloading OS-related IO from application related I/O.
Among major vendors:
- IBM competes in all categories:
- Super-heavy-weight
- POWER systems, which can run partitions with electrical isolation
but this is not widely used. Still that fits "super-heavyweight"
category as defined above.
- Heavy-weight
- Mainframes. Classic VM implementation is still famous
IBM's VM/CMS
That was the first successful commercial virtualization product that
was created when almost nobody even thought about virtualization.
- Power 5 and 6 Logical partitions (LPARs) fit the "heavyweight"
category and are extremely popular with AIX users (the technology
originated in classic IBM VM on System 3xx architecture which was the
first successful "heavy-virtualization" implementation). See
P5
virtualization
- Medium-weight (para-virtualization)
IBM sells servers with XEN preinstalled.
- IBM is weal in light-weight virtualization and missed the train. They
will catch it with AIX 6.
- IBM blade servers are slightly behind HP blades in factorization but
not by much
- Sun now competes in all five categories but its presence in heavyweight
category is simply symbolic as only recently this capability was made available.
Sun blade servers can mix and match both UltraSparc and Opteron-based blades.
- Microsoft competes mainly in two categories (heavy-weight virtualization
and para-virtualization)
- FreeBSD in just one category (light-weight virtualization) but it pioneered
this category.
- Linux vendors compete mainly in one category (para-virtualization using
Xen).
Conclusions
There is no free lunch and virtualization is not panacea.
It increases the complexity of environment and put severe stress of a single server
that host multiple instances on virtual machines. Failure of this server lead to
failure of all instances.
Therefore the natural habitat of virtualization is development,
test and stage servers as well as almost idle servers that servers various enterprise
consoles and similar low CPU intensive applications (Web servers and e-commerce
servers).
At the same time virtualization opens new capabilities
and sometimes it make sense to run a single instance of virtual machine on the server
to get such advantages as on the fly relocation of instances, virtual images manipulation
capabilities, etc. With technologies like Xen that claims less then 5% overhead
that approach becomes feasible. "Binary servers" -- servers that host just two applications
also look very promising.
Migration of rack-mounted servers to blade
servers is the most safe approach to server consolidation. Managers without experience
of work in partitioned environment shouldn’t underestimate what their administrators
need to learn and the set of new problems that virtualization creates One
good advice is "Make sure you put the training dollars in."
There are also other problems. A lot of software vendors
won’t certify applications as virtual environment compatible, for example VMware
compatible. In such cases running the application in virtual environment means that
you need to assume the risks and cannot count on vendor tech support to resolve
your issues.
All-in all virtualization is mainly played now in desktop
and low end servers space. It make sense to proceed slowly testing the water before
jumping in. Those that have adopted virtualization have, on average, only about
20% of their environment virtualized, according to IDC. VMware pricing structure
is a little bit ridiculous and nullifies hardware savings, if any. Their maintenance
costs are even worse. That means that alternative solutions like Xen3 or Microsoft
should be considered on Intel side and IBM and Sun on Unix side. As vendor consolidation
is ahead if you don’t have a clear benefit from virtualization today, you can wait
or limit yourself to "sure bets" like development, testing and staging servers.
The next version of Windows Server will put serious pressure on VMware in
a year or so. Xen is also making progress with IBM support behind it. With those
competitive pressures, VMware could become significantly less expensive in the future.
VMs are also touted as a solution to the computer security
problem. It's pretty obvious that they can improve security. After all, if you're
running your browser on one VM and your mailer on another, a security failure by
one shouldn't affect the other. If one virtual machine is compromised you can just
discard it and create an fresh image. There is some merit to that argument, and
in many situations it's a good configuration to use. But at the same time the transient
nature of Virtual Machines introduces new security and compliance challenges not
addressed by traditional systems management processes and tools. For example virtual
images are more portable and possibility of stealing the whole OS images and running
them on a different VM are very real. New security risks inherent in virtualized
environments need to be understood and mitigated.
Here is a suitable definition taken from the
article
published in Linux Magazine:
"(Virtual machines) offer the ability to
partition the resources of a large machine between a large number of users in
such a way that those users can't interfere with one another. Each user gets
a virtual machine running a separate operating system with a certain amount
of resources assigned to it. Getting more memory, disks, or processors is a
matter of changing a configuration, which is far easier than buying and physically
installing the equivalent hardware."
And FreeBSD and Solaris users has their lightweight VM built in
the OS. Actually FreeBSD jails, Solaris 10 zone and Xen are probably the most democratic
light weight VM. To counter the threat from free VMs VMware now produces a
free version too.
VMware Player
is able to run virtual machines made in VMware Workstation. There are many free
OS's on the website. Most of them are community made. There are also freeware tools
for creating VM's, mounting, manipulating and converting VMware disks and floppies,
so it is possible to create, run and maintain virtual machines for free (even for
commercial use).
Here is how this class of virtual machines is described in
Wikipedia
Conventional emulators like
Bochs emulate
the
microprocessor, executing each guest CPU instruction by calling a software
subroutine on the host machine that simulates the function of that CPU instruction.
This abstraction allows the guest machine to run on host machines with a different
type of microprocessor, but is also very slow.
An improvement on this approach is
dynamically recompiling blocks of machine instructions the first time they
are executed, and later using the translated code directly when the code runs
a second time. This approach is taken by
Microsoft's
Virtual
PC for
Mac OS X.
VMware Workstation takes an even more optimized
approach and uses the CPU to run code directly when this is possible. This is
the case for user mode and
virtual 8086 mode code on x86. When direct execution is not possible, code
is rewritten dynamically. This is the case for kernel-level and
real mode
code. In VMware's case, the translated code is put into a spare area of memory,
typically at the end of the address space, which can then be protected and made
invisible using the segmentation mechanisms. For these reasons, VMware is dramatically
faster than emulators, running at more than 80% of the speed that the virtual
guest OS would run on hardware. VMware boasts an overhead as small as 3%–6%
for computationally intensive applications.
Although VMware virtual machines run in user
mode, VMware Workstation itself requires installing various drivers in the host
operating system, notably in order to dynamically switch the
GDT and the
IDT tables.
One final note: it is often erroneously believed
that virtualization products like VMware or Virtual PC replace offending
instructions or simply run kernel code in user mode. Neither of these
approaches can work on x86. Replacing instructions means that if the code reads
itself it will be surprised not to find the expected content; it is not possible
to protect code against reading and at the same time allow normal execution;
replacing in place is complicated. Running the code unmodified in user mode
is not possible either, as most instructions which just read the machine state
do not cause an exception and will betray the real state of the program, and
certain instructions silently change behavior in user mode. A rewrite is always
necessary; a simulation of the current
program counter in the original location is performed when necessary and
notably hardware code
breakpoints
are remapped.
The Xen open source
virtual machine partitioning project is picking up momentum since acquiring the
backing of venture capitalists at the end of 2004. Now, server makers and Linux
operating system providers are starting to line up to support the project, contribute
code, and make it a feature of their systems at some point in the future. Work on
Xen has been supported by UK EPSRC grant GR/S01894, Intel Research, HP Labs and
Microsoft Research. Novell and Advanced Micro Devices also back Xen.
See
also
While everybody seemed to get interested in the
open source Xen virtual machine partitioning hypervisor just when
XenSource
incorporated and made its plans clear for the Linux platform, the
NetBSD variant
of the BSD Unix platform has been Xen-compatible for over a year now, and will
be as fully embracing the technology as Linux is expected to.
Xen has really taken off since Dec,
2004, when the leaders of the Xen project formed a corporation to sell and support
Xen and they immediately secured $6 million from venture capitalists Kleiner
Perkins Caufield & Byers and Sevin Rosen Funds.
Xen is headed up by Ian Pratt, a senior
faculty member at the University of Cambridge in the United Kingdom, who is
the chief technology officer at XenSource, the company that has been created
to commercialize Xen. Pratt told me in December that he had basically been told
to start a company to support Xen because some big financial institutions on
Wall Street and in the City (that's London's version of Wall Street for the
Americans reading this who may not have heard the term) insisted that he do
so because they loved what Xen was doing.
Seven years ago, Ian Pratt joined
the senior faculty at the University of Cambridge in the United Kingdom, and
after being on the staff for two years, he came up with a schematic for a futuristic,
distributed computing platform for wide area network computing called Xenoserver.
The idea behind the Xenoserver project is one that now sounds familiar, at least
in concept, but sounded pretty sci-fi seven years ago: hundreds of millions
of virtual machines running on tens of millions of servers, connected by the
Internet, and delivering virtualized computing resources on a utility basis
where people are charged for the computing they use. The Xenoserver project
consisted of the Xen virtual machine monitor and hypervisor abstraction layer,
which allows multiple operating systems to logically share the hardware on a
single physical server, the Xenoserver Open Platform for connecting virtual
machines to distributed storage and networks, and the Xenoboot remote boot and
management system for controlling servers and their virtual machines over the
Internet.
Work on the Xen hypervisor began in
1999 at Cambridge, where Pratt was irreverently called the "XenMaster" by project
staff and students. During that first year, Pratt and his project team identified
how to do secure partitioning on 32-bit X86 servers using a hypervisor and worked
out a means for shuttling active virtual machine partitions around a network
of machines. This is more or less what
VMware does
with its ESX Server partitioning software and its VMotion add-on to that product.
About 18 months ago, after years of coding the hypervisor in C and the
interface in Python, the Xen portion of the Xenoserver project was released
as Xen 1.0. According to Pratt, it had tens of thousands of downloads.
This provided the open source developers working on Xen with a lot of feedback,
which was used to create Xen 2.0, which started shipping last year. With the
2.0 release, the Xen project added the Live Migration feature for moving virtual
machines between physical machines, and then added some tweaks to make the code
more robust.
Xen and VMware's GSX Server and EXS
Server have a major architectural difference. VMware's hypervisor layer completely
abstracts the X86 system, which means any operating system supported on X86
processors can be loaded into a virtual machine partition. This, said Pratt,
puts tremendous overhead on the systems. Xen was designed from the get-go with
an architecture focused on running virtual machines in a lean and mean fashion,
and Xen does this by having versions of open source operating systems tweaked
to run on the Xen hypervisor. That is why Xen 2.0 only supports Linux 2.4, Linux
2.6, FreeBSD 4.9 and 5.2, and NetBSD 2.0 at the moment; special tweaks of NetBSD
and Plan 9 are in the works, and with Solaris 10 soon to be open-source, that
will be available as well. With Xen 1.0, Pratt had access to the source code
to Windows XP from Microsoft, which allowed the Xen team to put Windows XP inside
Xen partitions. With the future "Pacifica" hardware virtualization features
in single-core and dual-core Opterons and
Intel creating
a version of its "Vanderpool" virtualization hardware features in Xeon and Itanium
processors also being made for Pentium 4 processors (this is called "Silvervale"
for some reason), both Xen and VMware partitioning software will have hardware-assisted
virtual machine partitioning. While no one is saying this because they cannot
reveal how Pacifica or Vanderpool actually work, these technologies may do most
of the X86 abstraction work, and therefore should allow standard, compiled operating
system kernels run inside Xen or VMware partitions. That means Microsoft can't
stop Windows from being supported inside Xen over the long haul.
Thor Lancelot Simon, one of the key
developers and administrators at the NetBSD Foundation that controls the development
of NetBSD, reminded everyone that NetBSD has been supporting the Xen 1.2 hypervisor
and monitor within a variant of the NetBSD kernel (that's NetBSD/xen instead
of NetBSD/i386) since March of last year. Moreover, the foundation's own servers
are all equipped with Xen, which allows programmers to work in isolated partitions
with dedicated resources and not stomp all over each other as they are coding
and compiling. "We aren't naive enough to think that any system has perfect
security; but Xen helps us isolate critical systems from each other, and at
the same time helps keep our systems physically compact and easy to manage,"
he said. "When you combine virtualization with Xen with NetBSD's small size,
code quality, permissive license, and comprehensive set of security features,
it's pretty clear you have a winning combination, which is why we run it on
our own systems." NetBSD contributor Manuel Bouyer has done a lot of work to
integrate the Xen 2.0 hypervisor and monitor into the NetBSD-current branch,
and he said he would be making changes to the NetBSD/i386 release that would
all integrate /xen kernels into it and will allow Xen partitions to run in privileged
and unprivileged mode.
The Xen 3.0 hypervisor and monitor
is expected some time in late 2005 early 2006, with support for 64-bit Xeon
and Opteron processors. XenSource's Pratt told me recently that Xen 4.0 is due
to be released in the second half of 2005, and it will have better tools for
provisioning and managing partitions. It is unclear how the NetBSD project will
absorb these changes, but NetBSD 3.0 is expected around the middle of 2005.
The project says that they plan to try to get one big release of NetBSD out
the door once a year going forward.
Notes:
- Those pages are written by people for whom English is not a
native language. Some amount of grammar and spelling errors
should be expected.
- This is a Spartan WHYFF (We Help You For Free) site. It
cannot replace the best teachers and
the
best books.
- The site contain some obsolete pages as it develops like a
living tree... Some links on older pages
are broken. Please
try to use Google, Open directory, etc. to find a replacement link
(see
HOWTO search the WEB for details).
We would appreciate if you can
mail us a correct link.
|
|
Published: March 19 2008 |
FT.com
The combination of free software
from the likes of Linux and GNU with
virtualisation – which maximises
computing efficiency – is a
compelling proposition. It offers
lower costs, flexibility and greater
efficiency, plus environmental
benefits
Bogamil Balkansky, chief
of product marketing at VMWare, the
leading virtualisation vendor,
agrees that
vitualisation is
inherently green. “It helps shrink
the physical footprint and the
energy footprint,” he says. “For
every application running virtually,
the data centre saves about 7,000
kilowatt-hours a year.”
With virtual machine technology,
application workloads can be
consolidated to fewer servers and
they can be moved around, closed
down, opened up and re-provisioned
remotely with remarkable ease.
Until now, PCs and servers have
been vastly over-provisioned because
of software inflexibility and the
need to maintain some leeway in
hardware resources.
Mike Grandinetti, chief marketing
officer of Virtual Iron and senior
lecturer at MIT’s Sloan School of
Management, says: “Average server
capacity utilization is between 4
and 7 per cent.” Experts say we
might expect long-term capacity
utilization above 50 per cent, and
well beyond that for some
applications, but
the virtualisation
trend is only just getting started.
IBM is curing its own server
sprawl in a big green effort to
shrink 3,900 servers down to 33 z10
mainframes. “One z10 is equivalent
to 1,500 standard Intel x86 servers;
it takes up 85 per cent less space
and uses 85 per cent less power,”
says David Gelardi, IBM’s
vice-president of mainframes and
high performance computing.
The project is focused on
migrating IBM’s internal Unix
applications to applications running
in virtual machines upon zLinux,
which supports either Red Hat
Enterprise Linux (RHEL 4 or 5) or
Novell’s Suse Linux
Enterprise Server (SLES 9 or 10) as
host.
Alongside server consolidation,
GNU/Linux and virtualisation are
driving the Web 2.0 trend, which
sees businesses using the internet
to interact with customers and the
wider public.
Companies such as
Google,
Ebay,
Amazon and MySpace use
GNU/Linux to drive their services
and many use virtual machine
technology to provision applications
efficiently and allocate hardware
resources for customers.
There is hardly any debate that
by 2018 IT will consume more
aggregate kilowatt-hours than it did
in 2008, but by then data centres
will do so much more and desktops so
much less.
Mr Grandinetti of Virtual Iron
says: “There will be an explosion in
services without an explosion in
energy consumed.”
InformationWeek: I think
you see VMware
aggressively courting virtualization customers. Customers that I've spoken
with are
saying Microsoft is definitely coming from behind here. You mentioned it
on stage here. There's Hyper-V's delay. Does Microsoft's entrance now into the
virtualization space put it at a disadvantage in the virtualization world?
Ballmer: The choice is, you
know, to be first to have share or not. I guess I prefer to be first to have
share. Now, you've got to remember, this market has barely been scratched, less
probably in the install base -- less than 5% of all systems run virtually. Virtualization
is way too complicated, way too expensive today for people to take advantage
of it, and it's way too isolated from the rest of everything that happens in
application development to data center deployment and operations. That's not
my way of criticizing, it's just if we're going to get -- if the phenomenon
is going to fully take effect, then we've got to democratize it. That might
be VMware, [but] they haven't shown moves in that direction. Somebody could
argue it might be one of the
open source
alternatives. I like what we've got. I think we pay out on those problems.
That doesn't mean the other guys are going to go away. Obviously we recognize
that fact and we provide good interoperability with VMware's virtual machine.
But I don't think -- there's a simplicity with performance, with management,
integrated management, with everything else, I think we're going to make a real
difference. Sure, I wish we had everything we're announcing now and shipping
this year a year ago, sure. Two years ago? Sure. But, believe me. We're going
to make a big difference.
[Nov 12, 2007] Oracle’s virtual challenge to Windows and Red Hat
Matthew Aslett, November 12, 2007
VMware’s share price may have
taken a hit following the launch of
Oracle VM but the product has wider implications in the software market.
To some extent it is a software appliance play: like
Raw Iron without the iron. This question and answer from the
Q&A says it all:
“Does Oracle VM require a host operating system?
No. Oracle VM installs directly on server hardware and does not require
a host operating system.”
Oracle VM comes with pre-configured virtual machine images of Oracle
Database and Oracle Enterprise Linux and is designed to install directly
on the server hardware. It’s no surprise to find that the product is a development
of the
Unbreakable Linux group within Oracle. This makes sense given that it
is based on Xen and a lot of Oracle’s Xen expertise is within the Unbreakable
group, but also because it further disrupts the relationship between customers
and their operating system suppliers.
The target of Raw Iron was eradicating the layer of Microsoft Windows
that stood between Oracle and its customers’ hardware. Oracle VM targets
both Windows and Red Hat Enterprise Linux. Sure, you can run both as guest
operating systems on Oracle VM, but the customer’s first port of call becomes
Oracle. Whether the offering will make much of an impact outside Oracle-heavy
environments remains to be seen, however.
'You are absolutely deluded, if not stupid, if you think that a worldwide collection
of software engineers who can't write operating systems or applications without
security holes, can then turn around and suddenly write virtualization layers
without security holes.'
ParaFan writes "In a fascinating story on KernelTrap, Theo de Raadt asserts
that while virtualization can increase hardware utilization, it
does not in
any way improve security. In fact, he contends the exact opposite is true:
'You are absolutely deluded, if not stupid, if you think that a worldwide collection
of software engineers who can't write operating systems or applications without
security holes, can then turn around and suddenly write virtualization layers
without security holes.'
de Raadt argues that the lack of support for process
isolation on x86 hardware combined with numerous bugs in the architecture are
a formula for virtualization decreasing overall security, not increasing it."
VMware
Communities- ESX 3.0.1 Guests Freeze ...
Interesting term: Purple Screen of Death (VMware ESX
server crash). In this case all you virtual instances are hosed and you have a
small man-man disaster in your hands if there are more then 3 production
instances on the server.
"For virtualization to be prolific, there has to be a step up in terms of know-how.
"
August 02, 2007 |
Techworld
Open source virtualization developer XenSource has just inked a deal with
Symantec to collaborate on embedding Veritas Storage Foundation into XenEnterprise,
and delivering HA/DR and backup technology to XenSource's customers. In the
wake of that deal, founder and CTO Simon Crosby was in London recently to explain
the background to the deal. He also delivers his trenchant thoughts on the future
of the virtualization industry -- and launches a serious critique of VMware
and even of business partner Microsoft.
Q: How do you see the future of the virtualization market?
A: The world has created a new Microsoft -- there's a monster embedded
in our industry. So the market is starting to crystallize, partly as a consequence
of the way that VMware is building its company. They just want to sell more
and more, and it's starting to step on people's toes.
Q: Is VMware really that horrible? A: Unlike VMware, Microsoft
doesn't compete with its channel but leaves room for an ecosystem. It's a superb
platform player. Microsoft is very conscious of its scale and leaves pockets
of $100m markets around for its partners. Our relationship with Microsoft is
strong, will remain strong, and strengthens every day. Microsoft has been a
very supportive partner.
The chink in VMware's armor is the weakness of
its ecosystem -- all its partners are under threat. That said,
I wouldn't fault VMware entirely. VMware has grown very fast -- they had to
do that so I can't fault them for it, but no-one's making money out of VMware.
There's a general sense of unease.
Q: Will virtualization technology be absorbed into the OS?
A: There's plenty of scope for development. Microsoft's Viridian feature set
has been slashed because the features in the kernel of Server 2008 were fixed
and there was otherwise an overlap between it and Viridian. And Red Hat and
Novell haven't done much with Xen yet. None of the virtualization platforms
are anything but a way of virtualizing themselves.
We have managed to benefit from relationships on both sides.
Open source is a very clearly articulated argument -- it's about aligning a
community around a common codebase. Some of the open source software
(OSS) vendors compete with each other not with the bigger guys. OSS generates
pull-through because the customers get a richer set of services -- it's a longer
term play. We believe that the virtualization engine is a standard, commoditized
product that has to be open. It must address a range of CPUs, and have a big
hardware footprint.
It's also important not to make it the whole product so others get an incentive
to take it to market. We don't do an ESX [VMware's flagship product] -- that's
a car not an engine -- because an engine is more flexible, you can use it anywhere
and it gives space for others to develop, and they have financial incentives
to do so.
Q: Why is Microsoft not perceived as the big Satan now?
A: The
consent decree has changed things -- there are 1,400 lawyers at Microsoft.
In every conversation with them we find they're absolutely egalitarian about
access to APIs. They have huge market control but they realize they have to
embrace and manage open source. That means they have to interoperate and work
with it, because they know they can't eliminate it -- the world's changed. Also
they're huge so their ability to innovate gets clogged up, which leaves tons
of space for others to innovate -- they've learned to cooperate with others
in markets they can't get to.
Also, I think in terms of the scale of everything Microsoft does, virtualization
is only a minor project in a monster organization. Virtualization has become
the major shaping force in the industry -- and they [Microsoft] said that they
thought that more VMs meant more revenue but they're changing that as customers
need to know that it's OK to start Windows in a VM.
Q: Will this change? A: I don't know where they're going
with this -- it could be that things are taking longer. The policy is rational
but they haven't communicated that to the market yet. It's a huge opportunity
for someone to be make a product to manage licensing -- using technology used
for DRM and licensing so that you know how long an OS has run etc. It would
need to be an independent verifiable source for legal licensing.
Q: Will Xen continue to use the same technology in future -- in other
words, para-virtualization? A: Para-virtualization is an awful name:
if someone asks what would you rather have, full virtualization or para-virtualization,
what's your answer? The aim was to encourage OS vendors to make the OS ready
for virtualization -- but 95 percent of applications and OSes are legacy, unvirtualized.
Para-virtualization is relevant in another content
-- we use para-virtualized I/O and timers etc by inserting drivers etc into
Windows to get a fast stack working. From a product perspective, it means the
guest automatically installs the right software and it just works. We hook into
the HAL and get the best performance.
But most of the OSes aren't para-virtualized -- there's only RHEL 5 and SLES
10. The important thing is that in future every OS will be ready to run on a
hypervisor. [Intel's] VT gives us everything else.
Q: How do you see virtualization evolving over the next two years?
A: Hardware vendors will certify the hypervisor and it's up to the customer
to do everything else. Customers want to virtualized
everything else because the savings are so huge -- the confidence in virtualization
is high but it's too complex for the average guy.
On the client, virtualization technology has to be invisible and work using
[management] technology such as Intel's vPro. There also has to be a viable
ecosystem or it's a niche product.
The world will break into two camps: VMware, where you add more features
and sell more software, or open source. We're just a great component -- we do
a fantastic job of server virtualization working with best of breed partners
-- we plug into storage virtualization and it all works.
We have agreements with people such as Stratus and Marathon -- there's lots
we've not announced yet. Virtualization will be another category of IT admin
-- you'll find virtualization specialists much as you have database specialists
etc now.
Q: What about skill sets? A: Lack of skill sets is a major
barrier to take-up. We have over 300 certified partners, over 500 certified
trained partner engineers worldwide who train the trainers -- we have a course
that partners can resell. For virtualization to
be prolific, there has to be a step up in terms of know-how.
An important paper comparing performance of para-virtualization
approaches (eg Xen) with OS-level virtualization (jails). The authors shows
that jail-style virtualization has tremendous advantages in typical scenarios.
Hypervisors, popularized by Xen and VMware, are quickly becoming
commodity. They are appropriate for many usage scenarios, but there are scenarios
that require system virtualization with high degrees of both isolation and efficiency.
Examples include HPC clusters, the Grid, hosting centers, and PlanetLab. We
present an alternative to hypervisors that is better suited to such scenarios.
The approach is a synthesis of prior work on resource containers and security
containers applied to general-purpose, time-shared operating systems. Examples
of such container-based systems include Solaris 10, Virtuozzo for Linux, and
Linux- VServer. As a representative instance of container-based systems, this
paper describes the design and implementation of Linux-VServer. In addition,
it contrasts the architecture of Linux-VServer with current generations of Xen,
and shows how Linux-VServer provides comparable support for isolation and superior
system efficiency.
Write access to NTFS permits some using it virtual machines
"Normally Linux systems can only read from Windows NTFS partitions, but not
write to them which can be very annoying if you have to work with Linux and
Windows systems. This is where ntfs-3g comes into play. ntfs-3g is an open source,
freely available NTFS driver for Linux with read and write support. This tutorial
shows how to use ntfs-3g on a Fedora 7 desktop to read from and write to Windows
NTFS drives and partitions.
See also:
How To Use
NTFS Drives/Partitions Under Ubuntu Edgy Eft
Our-Picks: Access Your Linux Partitions Under Windows(Mar 05, 2007)
July 14, 2006 06:00 PM |
InformationWeek
IBM said Friday it will support Novell's Suse 10
Linux and Xen virtualization on its IBM's BladeCenter and other x86 hardware.
It will also allow management of Xen virtual machines under its Virtualization
Engine. That allows IBM customers to use familiar IBM management software to
provision and manage multiple Xen virtual machines.
Xen can convert a low-cost Intel or AMD processor-based server into multiple
virtual machines, each running a separate application. As freely available open-source
code, Xen is expected to play a major role
in server consolidation over the next few years. A consolidated server running
six or seven applications will achieve far higher utilization rates than one
running a single application.
IBM support is a plus for Novell, which is getting Linux out the door with
Xen
ahead of its competitor, Red Hat. Both have announced support for Xen on
their future Linux distributions. Novell on its Web site says it's putting "the
final touches" on its Suse 10 distribution.
Red Hat plans to offer a distribution including Xen 3.0
late this year. IBM says the company will support Xen running on Red Hat
Linux when Red Hat gets its distribution out containing Xen 3.0.
Xen was originally developed at Cambridge University in England, and its
originators formed XenSource, a commercial company, to provide technical support
for its adoption.
As a more mature Xen version 3.0 approached release last year, the virtualization
market leader, VMware, made a bid to compete with the open-source code by making
VMware Server, a base-level, single-server virtualization product, available
free. VMware, an independent business unit of EMC, reported revenues of $157
million in its second quarter of 2006, a growth rate of 73%. If revenues continue
at that pace for four quarters, VMware will become a $630 million-a-year software
company. EMC hasn't previously broken out revenue figures for VMware.
IBM, HP, and Sun Microsystems(SUNW)
are lined up behind open-source Xen as a way of bidding for part of the burgeoning
virtualization software revenues currently commanded by VMware.
Probably the fastest way to run Linux under Windows. It works (you need to connect
to virtual mashine via VNC -- no screen sharing).
Virtualization with VMware, Xen, and Kernel-based Virtual
Machine (KVM) are all the rage these days. But did you know that you can run
Linux cooperatively with Microsoft Windows? This article explores Cooperative
Linux (coLinux), starting with a quick introduction to virtualization and then
looking at the approach taken by coLinux. You'll also see how to get coLinux
up and running on Windows.
For systems virtualization, products and product marketing have given us several
variations on the theme of "one system pretending to be many systems". These can
be segregated into several categories, as follows.
- Hardware partitioning -- This method involves the strict division
of a system into fixed collections of CPUs. Those CPUs get their own operating
system installed on them and run independently of the other partitioned CPUs
on the system. Note that hardware partitioning has been available to Sun customers
for many years, in the form of hardware domains on the enterprise servers. These
servers also include an advanced form of hardware partitioning that can move
CPUs between partitions -- Sun calls it "dynamic reconfiguration". Dynamic reconfiguration
still partitions the system into separate groups of CPUs, and the resource movement
is on large time scales (hours or days), so it deserves a separate category
from the other forms of virtualization discussed below. Hardware partitioning
virtualization is also newly available in the T1 chip (as found in the T1000
and T2000 serves. The T1 chip sports a "logical domain" facility as of the Solaris
10 11/06 release. The T1-based systems can now create up to 32 LDoms, each of
which can have its own Solaris 10 installed and running. It could be argued
that this physical partitioning of a system is not really virtualization, but
it does involve one system acting like many so it is included here. See
Figure 1A .
- Normal virtualization (also called operating system virtualization)
-- This setup has hardware or software, the "hypervisor", acting like the bare
metal of the system, allowing for example multiple operating systems to be installed
on the same system. The virtual machines see only the virtual bare metal, and
therefore do not realize they are virtualized. The hypervisor then manages the
resources to share them amongst the virtual machines. Sometimes this resource
management is basic (e.g., virtual machine A gets four CPUs and machine B gets
two CPUs) and sometimes more advanced. Note that there is complexity to this
solution. For example, many aspects of the bare metal virtualization involve
emulating hardware facilities, such as page tables and interrupt vectors. VMware
Workstation and ESX are examples of this type of virtualization. See
Figure 1B .
- Paravirtualization -- This is a cooperative solution in which the
virtualization technology exposes an API to the operating systems running on
top of it. That API allows the virtualized OS to ask the paravirtualizing hypervisor
to perform tasks for it (e.g., change a page table entry). In this case the
complexity is reduced and, potentially, performance can be gained. However,
the virtualized operating system must be modified to call the hypervisor's API.
Therefore, the operating systems being virtualized must volunteer for that duty,
and non-volunteers (i.e., Windows) are not invited to play. Xen and VirtualIron
are examples of this type of virtualization. See
Figure 1C .
- Hardware-assisted virtualization -- This setup improves both normal
and paravirtualization by giving the hypervisor help in emulating the base hardware.
With hardware assist, such as the Intel VT and AMD-V (as found in the Sun Opteron
"M2" servers), there is less emulation and interception by hypervisors. For
example, Xen could not run Windows in a virtual machine before Intel VT and
AMD-V came along.
- Containers -- Containers, as found in Solaris 10 and beyond, and
BSD "jails" belong in a separate category from the other technologies. They
draw the virtualization line not between the operating system and the hardware
but rather between the applications and the operating system. In this manner,
applications can run in virtual containers on top of one operating system. This
form of virtualization is less flexible than the standard models in that there
is one kernel running and all applications run within that one kernel (and kernel
patch set). But before condemning them as too restrictive, consider the Solaris
project "BrandZ" (http://www.opensolaris.org/os/community/brandz/),
which will allow other operating systems to run (virtually, of course) with
a Solaris Container.
February 14th, 2007
ZDNet.com
Red Hat plans to squeeze VMware on pricing as it bundles
virtualization technology with its operating system.
... Crenshaw argues that with current VMware software a
customer buys software from VMware and then has to buy more operating system
licenses for each instance virtualized. By combining the operating system–in
this case Red Hat–with virtualization technology those additional licenses aren't
necessary.
...Red Hat will also aim to simplify pricing with virtualization.
"We will have everything you need to virtualize your environment into one SKU.
It will be much more economical than buying separate components," says Crenshaw.
Red Hat's target is pretty clear. For instance, VMware
Infrastructure 3 comes in three editions–starter, standard and enterprise–with
prices ranging from $1,000
per two processors to $5,750. Support and upgrade subscriptions boost those
totals.
...KVM appears to be on the fast path. This project first surfaced in October
2006; it found its way into the 2.6.20 kernel a few months later. On 25 February,
KVM 15 was announced. This release has an interesting new feature: live migration.
The speed with which the KVM developers have been able to add relatively advanced
features is impressive; equally impressive is just how simple the code that
implements live migration is.
KVM starts with a big advantage over other virtualisation projects:
it relies on support from the hardware, which is
only available in recent processors. As a result, KVM will not
work on the bulk of currently deployed systems. On the other hand, designing
for future hardware is often a good idea -- the future tends to come quickly
in the technology world.
By focusing on hardware-supported virtualisation, KVM is able to concentrate
on developing interesting features to run on the systems that companies are
buying now.
The migration code is built into the QEMU emulator; the relevant source file
is less than 800 lines long.
You need to calculate saving to avoid spending more money then with an old
solution. Also large servers are really expensive so hardware saving might be
illusionary. You should always consider blades as an alternative.
The big day arrives -- after months of planning
Re:Yawn
(Score:5, Informative)by giminy (94188) on Friday March 09, @02:16PM (#18292472)
We took a system that according to our monitoring sat at essentially 0-1% used (load average: 0.01, 0.02, 0.01) and put it on a virtual.(http://www.readingfordummies.com/blog/ | Last Journal: Thursday November 21, @05:10PM)
Load average is a bad way of looking at machine utilization. Load average is the average number of processes on the run queue over the last 1,5,15 minutes. Programs running exclusively I/O will be on the sleep queue while the kernel does i/o stuff, giving you a load average of near-zero even though your machine is busy scrambling for files on disk or waiting for network data. Likewise, a program that consists entirely of NOOPs will give you a load average of one (+1 per each additional instance) even if its nice value is all the way up and it is quite interruptable/is really putting zero strain on your system.
Before deciding that a machine is virtualizable, don't just look at load average. Run a real monitoring utility and look at iowait times, etc.
Reid
(http://www.spamgourmet.com/) Load average is a bad way of looking at machine utilization. Load average is the average number of processes on the run queue over the last 1,5,15 minutes.
This may be wrong, but I've always looked at load as the number of processes waiting for resources (usually disk, CPU, or network).
I've seen boxes with issues that have had a number of processes stuck in the nonkillable D (disk) wait state that were just stuck, but they had no real impact on the system besides artifically running the load up.
I've also seen where load was reported as N/NCPUs and N regardless of the number of CPUs.
Like all statistics, any single number in isolation is just a number. Even if the real meaning is the average number of processes in the run queue, that does not tell you much. Thinking of it as the number of processes waiting for some piece of hardware seems more accurate.
(http://coherentnetworksolutions.com/) Well, disks may not be a great example. VMWare is of course a product of EMC, which makes (drumroll) high end SAN hardware and software management tools. While Im not quite saying that there is a clear conflict of interest here, the EMC big picture is clear: "now that you have saved a metric shit load of cash on server hardware, spend some of that on a shiny new SAN system". The nicer way of that is that both EMC SANs and VMware do the same thing: consolidation of hardware onto better hardware, abstraction of services provided, finer grained allocation of services, shared overhead - and management.
If spikes on one VM are killing the whole physical host, then you are surely doing something wrong. Perhaps you do need that SAN with very fast disk access. Perhaps you need to schedule migration of VMs from one physical host to another when your report server pegs the hardware. Or, if its an unscheduled spike, you need to have rules that trigger migration if one VM is degrading service to others.
(Score:2, Interesting)
by dthable (163749) <dhable AT uwm DOT edu> on Friday March 09, @01:11PM (#18291506)(Last Journal: Monday February 12, @01:59PM)
I could also see their use when upgrading or patching machines. Just take a copy of the virtual image and try to execute the upgrade (after testing, of course). If it all goes to hell, just flip the switch back. Then you can take hours trying to figure out what went wrong instead of being under the gun.
(Score:4, Interesting)
by afidel (530433) on Friday March 09, @01:55PM (#18292162)Well, our Oracle servers are DL585's with four dual core cpu's, 32GB of ram, dual HBA's backed by an 112 disk SAN and they regularly max out both HBA's, trying to run that kind of load on a VM just doesn't make sense with the I/O latency and throughput degradation that I've seen with VMWare. I know I'm not the only one as I have seen this advice from a number of top professionals that I know and respect. If you have a lightly loaded SQL server or some AD controllers handling a small number of users then they might be good candidates, but any server that is I/O bound and/or spends a significant percentage of the day busy is probably the lowest priority to try to virtualize. You can probably get 99+% of the benefit of virtualization from the other 80-90% of your servers that are likely good candidates.
(http://www.yafla.com/dforbes/ | Last Journal: Tuesday September 27, @10:43AM)
Indeed, it has become a bit of a unqualified, blanket meme: "Don't put database servers on virtual machines!" we hear. I heard it just yesterday from an outsourced hardware rep for crying out loud (they were trying to display that they "get" virtualization).
Ultimately, however, it's one of those easy bits of "wisdom" that people parrot because it's cheap advice, and it buys some easy credibility.
Unqualified, however, the statement is complete and utter nonsense. It is absolutely meaningless (just because something can superficially get called a "database" says absolutely nothing about what usage it sees, its disk access patterns, CPU and network needs, what it is bound by, etc).
An accurate rule would be "a machine that saturates one of the resources of a given piece of hardware is not a good candidate to be virtualized on that same piece of hardware" (e.g. your aforementioned database server). That really isn't rocket science, and I think it's obvious to everyone. It also doesn't rely upon some meaningless simplification of application roles.
Note that all of the above is speaking more towards the industry generalization, and not towards you. Indeed, you clarified it more specifically later on.
(Score:2)
by Courageous (228506) on Friday March 09, @03:23PM (#18293384)Well. VMWare has issues with IO latency. One has to watch for that, not try to virtualize everything. But. You say "Virtualization bad" for "CPU intensive," and I cannot agree with that. SPECint2006 and SPECfp2006, as well as rates are within 5% of hard metal for ESX. I've run the tests myself. Old school "CPU intensive" applications are a non-conversation in in virtualizaation today.
It's the network IO and network latency that will kill you if you don't know what you're doing. VMWare has known issues in that area (although they must break through these entirely or 10GE will never work properly in VMWare). One can work around these issues, however I'd simply say it's a Best Practice to simply plan to "not virtualize everything." I'd say target 65%-ish of your compute infrastructure in preplanning and base your real decisions on an actual analysis.
C//
(Score:5, Informative) by Semireg (712708) on Friday March 09, @12:59PM (#18291308)
As for "putting many workloads on a box and uptime," this writer should really take a look at VMware VI3 and Vmotion. Not only can you migrate a running VM without downtime, you can "enter maintenance mode" on a physical host, and using DRS (distributed resource scheduler) it will automatically migrate the VMs to hosts and achieve a load balance between CPU/Memory. It's crazy amazing(TM).
Lastly, just to toot a bit of the virtualization horn... VMware's HA will automatically restart your VMs on other physical hosts in your HA cluster. It's not unusual for a Win2k3 VM to boot in under 20 seconds (VMware's BIOS posts in about
Virtualization is Sysadmin Utopia. -- cvl, a Virtualization Consultant
(Score:2) by div_2n (525075) on Friday March 09, @02:05PM (#18292314) I'm managing VI3 and we use it for almost everything. Ran into some trouble with one antiquated EDI application that just HAD to have a serial port. That is a long discussion, but for reasons I'm quite sure you could guess, I offloaded it to an independent box. We run our ERP software on it and the vendor has tried (unsuccessfully) several times to blame VMWare for issues.
You don't mention it, but consolidated backup just rocks. I have some external Linux based NAS machines that use rsync to keep local copies of both our nightly backups and occasional image backups at both sites.
Thanks to VMWare, it's like I've told management--"Our main facility could burn to the ground and I could have our infrastructure back up and running at our remote site before the remains stop smoldering much less get a check from the insurance company."
(Score:5, Insightful)
by cbreaker (561297) on Friday March 09, @01:38PM (#18291910)(Last Journal: Tuesday December 12, @07:54PM)
Indeed. If you have a proper ESX configuration: At least two hosts, SAN back-end, multiple NIC's, supported hardware - you'll find that almost none of the points are valid.
Teaming, hot-migrations, resource management, and lots of other great tools make modern x86 virtualization really enterprise caliber.
I think that the people that see it as a toy are people that have never used virtualization in the context of a large environment, being used properly with proper hardware. You can virtualize almost any server if you plan properly for it.
In the end, by going virtual you end up actually removing so much complexity from your systems that you'll never know how you did it before. No longer does each server have it's own drivers, quirks, OpenManage/hardware monitor, etc etc. You can create a new VM from a template in 5 minutes, ready to go. You can clone a server in minutes. You can snapshot the disks (and RAM, in ESX3) and you can migrate them to new hardware without bringing them down. You can create scheduled copies of production servers for your test environment. So much more simple then all-hardware.
I'll admit that you shouldn't use virtual servers for everything (yet) but you will eventually be able to run everything virtual, so it's best to get used to it now.
(Score:4, Interesting)
by DesertBlade (741219) on Friday March 09, @12:51PM (#18291170)Good story, but I disagree in some areas.
Bandwidth concerns. You can have more than one NIC installed on the server and have it dedicated to each virtual machine.
Downtime: If you need to do maintance on the host that may be a slight issue, but I hardly ever have to anything to the host. Also if the host is dying, you can shut donw the Virtual machine and copy it to another server (or move the drive) and bring it up fairly quickly. You also have cluster capability with virtualization.
(Score:2) by QuantumRiff (120817) on Friday March 09, @12:52PM (#18291196) If your servers become toast, due to whatever reason, you can get a simple workstation, put a ton of RAM in it, and load up your virtual systems. Of course they will be slower, but they will still be running. We don't need to carry expensive 4 hour service contracts, just next business day contracts, saving a ton of money. The nice thing for me with Virtual servers is it is device agnostic, so if I have to recover, worst case, I have only one server to worry about NIC drivers, RAID settings/drivers, etc. After that, its just loading up the virtual server files.
(Score:1) by bigredradio (631970) on Friday March 09, @01:08PM (#18291444)
(http://www.storix.com/ | Last Journal: Sunday August 20, @03:39PM) Sort of... I agree that you can limit hardware needs, but you also have a central point of failure. If the host OS or local storage goes, you now have lost multiple systems instead of one. One issue I have seen is having external scsi support. At least with Xen, you cannot dynamically allocate a pci scsi card to each node. This may also hold true for fiber channel cards.(not sure). That means, no offsite tape backups for the individual nodes and no access to SAN storage through the virtual nodes.
(Score:1, Interesting) by Anonymous Coward on Friday March 09, @12:56PM (#18291262) The absolute only place it has not been appropriate are locations requiring high amounts of disk IO. It has been a godsend everywhere else. All of our web servers, application servers, support servers, management servers, blah blah blah. It's all virtual now. Approximately 175 servers are now virtual. The rest are huge SQL Server/Oracle systems.
License controls are fine. All the major players support flexible VM licensing. The only people that bark about change control are those who simply don't understand virtual infrastructure and a good sit-down solved that issue. "Compliance" has not been an issue for us at all. As far as politics are concerned -- if they can't keep up with the future, then they should get out of IT.
FYI: We run VMware ESX on HP hardware (DL585 servers) connected to an EMC Clariion SAN.
(Score:2, Insightful) by 7bit (1031746) on Friday March 09, @12:59PM (#18291316) I find Virtualization to be great for home use.
It's safer to browse the web through a VM that is set to not allow access to your main HD's or partitions. Great for any internet activity really, like P2P or running your own server; if it gets hacked they still can't affect the rest of your system or data outside of the VM's domain. It's also much safer to try out new and untested software from within a VM, in case of virus or spyware infection, or just registry corruption or what have you. I can also be useful for code developement within a protected environment.
Did I mention portability? Keep back-up's of your VM file and run it on any system you want after installing something like the Free VMWare Server:
http://www.vmware.com/products/server/ [vmware.com]
(Score:3, Interesting)
by micromuncher (171881) on Friday March 09, @01:14PM (#18291556)The article mentions a point of common sense that I fought tooth 'n nail about and lost in the Big Company I'm at now.
For a year I fought against virtualizing our sandbox servers because of resource contention issues. One machine pretending to be many with one NIC and one router. We had a web app that pounded a database... pre virtualization it was zippy. Post virtualization it was unusuable. I explained that even though you can Tune virtualized servers, it happens after the fact, and it becomes a big active management problem to make sure your IT department doesn't load up tons of virtual servers to the point it affects everyone virtualized. They argued, well, you don't have a lot of use (a few users, and not a lot of resource utilization.)
My boss eventually gave in. The client went from zippy workability in an app being developed, to slow piece of crap because of resource contention, and its hard to explain that an IT change forced under the hood was the reason for SLOW, and in UAT, SLOW = BUSTED.
That was a huge nail in the coffin for the project. When the user can't use the app on demand, for whatever reason, and they don't want to hear jack about tuning or saving rack space.
So all you IT managers and people thinking you'll get big bonuses by virtualizing everything... consider this... ONE MACHINE, ONE NETWORK CARD, pretending to be many...
(Score:5, Insightful)
by LodCrappo (705968) on Friday March 09, @01:28PM (#18291790)(http://www.spogbiper.com/)
Increased uptime requirements arise when enterprises stack multiple workloads onto a single server, making it even more essential to keep the server running. "The entire environment becomes as critical as the most critical application running on it," Mann explains. "It is also more difficult to schedule downtime for maintenance, because you need to find a window that's acceptable for all workloads, so uptime requirements become much higher."
No, no, no. First of all, in a real enterprise type solution (something this author seems unfamiliar with) the entire environment is redundant. "the" server? You don't run anything on "the" server, you run it on a server and you just move the virtual machine(s) to another server as needed when there is a problem or maintenance is needed. It is actually very easy to deal with hardware failures.. you don't ever have to schedule downtime, you just move the VMs, fix the broken node, and move on. For software maintenance you just snapshot the image, do your updates, and if they don't work out, you're back online in no time.
In a physical server environment, each application runs on a separate box with a dedicated network interface card (NIC), Mann explains. But in a virtual environment, multiple workloads share a single NIC, and possibly one router or switch as well.
Uh... well maybe you would just install more nics? It seems the "expert" quoted in this article has played around with some workstation level product and has no idea how enterprise level solutions actually work.
The only valid point I find in this whole article is the mention of additional training and support costs. These can be significant, but the flexibility and reliability of the virtualized environment is very often well worth the cost.
(Score:2) by 15Bit (940730) on Friday March 09, @03:17PM (#18293318) It will depend what you do with your 3 shuttles.
I just ditched my dual opteron (linux) + shuttle (windows) setup and replaced it with a single Core Duo box with linux virtualized under WinXP. I'm running the VMware free server software (http://www.vmware.com/products/free_virtualizatio
n.html [vmware.com]) and i have to say i'm impressed.
The only negatives i've found so far (aside from the obvious ones related to two systems in one computer) are some slowdown in mouse responsiveness in the virtualized linux and the lack of hardware accelerated graphics (these might be the same thing, i don't know). You also have to turn off access of the virtualized OS to the DVDROM or everything gets confused.
The positives are that it was piss easy to set up and really "just works". The VMware'd linux talked to my network card without intervention and happily picked up a unique IP from my DHCPD. NIS/NFS to my fileserver "just worked". I can allocate the VMware OS 1 or 2 cores and vary the amount of RAM it sees. My main use for the linux V/OS is molecular dynamics simulations, the software running message passing via LAM/MPI and all compiled under Intel C and Fortran Compilers. Again, all of that "just worked".
In terms of performance, MD calcs done on 1 cpu seem to be at close to full speed for one core, but running them dual gives only an 80% scaling improvement. That slowdown is about as expected, given that there's another OS running. Another nice side benefit is that i can run an MD calc on 1 cpu and play games with the other. I don't notice any lag.
So to summarise - if i'd paid money for VMware i'd be seriously impressed, but for something to do exactly what i want for free is truly amazing.
(Score:1) by Gazzonyx (982402) on Friday March 09, @03:19PM (#18293356) I've found that virtualization is a nice buffer zone from management decisions! Case in point, yesterday my boss (he's got a degree in comp. sci - 20 years ago...), who's just getting somewhat used to the linux server that I set up, decided that we should 'put
/var in the
/data directory tree'; I had
folded once when he wanted to put
/home in /data,
for backup reasons, and made it a symlink from /.
Now when he gets these ideas, before just going and doing it on the production server, I can say "How about I make a VM and we'll see how that goes over", thinking under my breath the words of Keith Moon, "That'll go over like a lead zeppelin". It give me a technology to leverage where I can show that an idea is a Bad Idea, without having to trash the production server to prove my point.
I've even set up a virtual network (1 samba PDC and 3 windows machines), to simulate our network on a small scale to set up proof of concepts. If they don't believe that something will work, I can show them without having their blessing to mess with our network. If it doesn't work, I roll back to my snapshots, and I have a virgin virtual network again.Does anyone do this? Has it worked out where you can do a proof of concept that otherwise, without virtualization, you would be confined to whiteboard concepts that no one would listen to?
(Score:2, Interesting)
by dthable (163749) <dhable AT uwm DOT edu> on Friday March 09, @01:17PM (#18291608)
And if the software doesn't require a dedicated machine, the IT department wants one. The company I used to work for would buy a new machine for every application component because they didn't want Notes and a homegrown ASP application to conflict with each other. Seemed like a waste of hardware in my opinion.(Last Journal: Monday February 12, @01:59PM)
(Score:2)
by fyngyrz (762201) * on Friday March 09, @05:38PM (#18295052)
(http://www.blackbeltsystems.com/ | Last Journal: Saturday January 27, @06:16PM)
Examine that quote from the article closely. See anything there that indicates virtualization "doesn't work"? No, nor do I. What they are talking about here has nothing to do with how well virtualization works, what they're complaining about is that a particular tool requires competence to use well in various work environments. Well, no one ever said that virtualization would gift brains to some middle level manager, or teach anyone how to use an office suite, or imbue morals and ethics into those who would steal; virtualization lets you run an operating system in a sandbox, sometimes under another operating system entirely. And it does that perfectly well, or in other words, it works very well indeed. I call FUD.