About Virtual Volumes
Virtual volumes are a virtualization of the physical volumes that storage servers can access.
In its most elemental form, a virtual volume is similar to a logical partition of a physical disk. SANmelody software imparts several beneficial attributes to virtual volumes that improve on the flexibility, performance, reliability, and availability of these resources while substantially reducing their administrative overhead. SANmelody virtual volumes can represent space on one or multiple physical disks in the NMV pool. There can be many disks or partitions of disks grouped together to form a single large volume. They can even represent huge virtual images that far exceed the amount of disk space available in the pool at a given point in time. When configured for high availability, virtual volumes can remain operational even in the event that some of the physical resources fail, or a path to the disk is disrupted.
A virtual volume can be comprised of one or two volumes in a set. A virtual volume comprised of one volume is a linear virtual volume, this is the most basic virtual volume. If a virtual volume is comprised of two volumes, it is a mirror which provides fault tolerance to your SAN. Linear virtual volumes or mirrors can then be mapped to application servers where they are seen as physical disks and can be partitioned, assigned drive letters and used as any standard storage would be.
Virtual volumes that are mirrored (comprised of two volumes) can have certain path attributes. Setting multi-path attributes (including Alternate Path, 3rd Party Alternate Path, MPIO, or Cluster Path) for the mirrors add High Availability (HA) to your SAN.
See also:
Virtual Volume Properties
About Alternate Pathing and MPIO