HP 3PAR InForm OS 3.1.1 CLI Administrator's Manual

Virtual volumes 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 a 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 a 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 HP 3PAR Virtual Copy Software 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.
For greater administrative flexibility, you can provision the virtual volume’s user space and snapshot
space from the same or different CPGs. If the virtual volume’s user space and snapshot space are
on a different CPGs, the user space remains available to the host if the CPG containing the snapshot
space becomes full. To save time by not repeating tasks, you can create many identical virtual
volume’s at one time. For planning information about virtual volumes and copies of volumes, refer
to the HP 3PAR InForm OS Concepts Guide.
Fully-Provisioned Virtual Volumes
A fully-provisioned virtual volume is a volume that uses logical disks that belong to a logical disk
pool known as a Common Provisioning Group (CPG). Fully-provisioned virtual volumes are the
default system volume and do not require any additional licenses. Unlike Thinly-Provisioned Virtual
Volumes (TPVVs), fully-provisioned virtual volumes have a set amount of user space allocated in
the system for user data. They require the system to reserve the entire amount of space required
by the fully-provisioned virtual volume wether or not the space is actually used. The fully-provisioned
virtual volume size is fixed, and the size limit is 16 TB. You can set snapshot space allocation limits
and usage warnings to help manage the growth of snapshot space. For detailed information about
fully-provisioned virtual volumes, see the HP 3PAR InForm OS Concepts Guide.
NOTE: Some fully-provisioned virtual volumes may be designated as a CPVV in the 3PAR InForm
CLI.
Thinly-Provisioned Virtual Volumes
With an HP 3PAR Thin Provisioning Software license, you can also create Thinly-Provisioned Virtual
Volumes (TPVVs). A TPVV uses logical disks that belong to a logical disk pool known as a Common
Provisioning Group (CPG). TPVVs associated with the same CPG draw user space from that pool
as needed, allocating space on demand in chunklets. As the volumes that draw space from the
CPG require additional storage, the system automatically creates additional logical disks and adds
them to the pool until the CPG reaches the user-defined growth limit that restricts the CPG’s maximum
size. The TPVV volume size limit is 16 TB. For detailed information about TPVV growth warnings
and growth limits, see the HP 3PAR InForm OS Concepts Guide.
Virtual Volume Types 85