HP 3PAR StoreServ Concepts Guide: HP 3PAR OS 3.1.3

9 Virtual Volumes
Overview
Volumes draw their resources from CPGs, and volumes are exported as LUNs to hosts. Virtual
volumes are the only data layer visible to hosts. You can create physical copies or virtual copy
snapshots of virtual volumes for use if the original base volume becomes unavailable. Before
creating virtual volumes, you must first create CPGs to allocate space to the virtual volumes. For
information about CPGs, see “Common Provisioning Groups” (page 41).
You can organize volumes into autonomic groups that can be managed as one volume. If you
have a group of volumes that require the same administrative procedures, it is easier to group
those volumes into an autonomic group and manage them together.
Virtual volumes can be created by using both the HP 3PAR CLI and the HP 3PAR Management
Console. See the HP 3PAR Command Line Interface Administrator’s Manual and the HP 3PAR
Management Console Online Help for instructions on performing these tasks.
For the maximum number of virtual volumes and virtual volume copies that can be created with
your specific system configuration, go to the SPOCK website:
http://www.hp.com/storage/spock
NOTE: Creating TPVVs requires the HP 3PAR Thin Provisioning Software license. Creating virtual
copies requires the HP 3PAR Virtual Copy Software license. For more information, see “HP 3PAR
Software” (page 10).
Virtual Volume Types
There are three types of virtual volumes:
• FPVVs
• TPVVs
• Administrative volumes
Administrative volumes are created by the system and are for system usage only.
FPVVs and TPVVs have three separate data components:
• User space is the area of the volume that corresponds to the LD regions in the CPG that are
available to the host. The user space contains the user data and is exported as a LUN to the
host.
• Snapshot space, or copy space, is the area of the volume that corresponds to LD regions in
the CPG that contain copies of user data that changed since the previous snapshot. The
snapshot space contains the copy data.
• Administration space, or admin space, is the area of the volume that corresponds to LD regions
in the CPG that track changes to the volume since the previous snapshot was created. The
administration space contains pointers to copies of user data in the snapshot space.
Administration space is managed by the system, not with the tools you use to manage user
and snapshot space.
You can increase the size of volumes, the amount of user space, and the amount of snapshot space
for volumes as the requirements increase. If the user space and snapshot space use all available
space, the copy-on-write operation of the Virtual Copy feature will fail. To avoid running out of
user space, use TPVVs to automatically draw more user space from a CPG. The HP 3PAR OS
automatically reclaims unused snapshot space from TPVVs and FPVVs and returns the space to the
LDs.
For greater administrative flexibility, you can provision the virtual-volume user space and snapshot
space from the same or different CPGs. If the virtual-volume user space and snapshot space are
44 Virtual Volumes