Solaris Volume Manager is a software the enables to create, modify and use RAID-0 (concatenation and stripe) volumes, RAID-1 (mirror) volumes, RAID 0+1 volumes, RAID 1+0 volumes, RAID-5 volumes, and soft partitions.
Since Solaris 9 Solaris Volume Manager has been included as a standard part of the Solaris operating system and works with UFS. In Solaris 10 SVM is superseded by ZFS.
Soft partitioning and automatic device relocation make the Solaris Volume Manager software a viable candidate for your storage management needs. Solaris Volume Manager features enhance storage management capabilities beyond what is handled by intelligent storage arrays with hardware RAID. Here is the list of features from Solaris OpenSolaris.org
Here's a link to a Sun white paper that talks about it:
wwws.sun.com/software/whitepapers/solaris9/volume_manager.pdf
The Volume Manager software creates virtual disks (volumes) out of physical disks or partitions to be exact: volumes are built from disk partitions (slices is Solaris terminology). A Volume is a name for a group of slices that appear to the system as a single, logical device (virtual disk). There are also called “metadevices” but more correct term is “volumes”. Functionally volume is the same as a physical disk from the applications view: SVM converts all I/O requests directed at a volume into I/O requests to the underlying member partitions.
You create a volume as a RAID 0 (concatenation or stripe) volume, a RAID 1 (mirror) volume, a RAID 5 volume, a soft partition, or a UFS logging volume.
You can use either the Enhanced Storage tool within the Solaris Management Console or the command-line utilities to create and administer volumes.