HP 3PAR InForm OS 3.1.1 Concepts Guide

10 Virtual Volumes
Overview
Volumes draw their resources from Common Provisioning Groups (CPGs), and volumes are exported
as Logical Unit Numbers (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 40).
Volumes can be grouped 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 mange them together.
Creating virtual volumes can be performed with both the HP 3PAR InForm OS Command Line
Interface (CLI) and the HP 3PAR InForm Management Console. Refer to the HP 3PAR InForm OS
CLI Administrator’s Manual and the HP 3PAR InForm OS Management Console Online Help for
instructions on how to perform 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 Single Point of Connectivity Knowledge (SPOCK)
website http://spock.corp.hp.com/index.aspx.
NOTE: Creating Thinly-Provisioned Virtual Volumes (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 InForm OS Software” (page 15).
Virtual Volume Types
There are three types of virtual volumes:
• Fully-provisioned virtual volumes
• Thinly-Provisioned Virtual Volumes (TPVVs)
• Administrative Volumes
Administrative volumes are created by the system and are for system usage only.
Fully-provisioned virtual volumes and TPVVs have three separate data components:
• User space is the area of the volume that corresponds to the logical disk regions in the CPG
available to the host. The user space contains the user data and is exported as a LUN to the
host.
• Snapshot space, also known as copy space, is the area of the volume that corresponds to
logical disk regions in the CPG containing copies of user data that changed since the previous
snapshot of the volume was created. The snapshot space contains the copy data.
• Administration space, also known as admin space, is the area of the volume that corresponds
to logical disk 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 Virtual Copy feature’s copy-on-write operation will fail. To avoid running out of user
space, use TPVVs to automatically draw more user space from a CPG. The InForm OS automatically
reclaims unused snapshot from TPVVs and fully-provisioned virtual volumes and returns the space
to the logical disks.
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