HP 3PAR StoreServ 7450 4-node HP 3PAR StoreServ Storage Concepts Guide (OS 3.1 - Page 43

Administrative Volumes, Fully-provisioned Virtual Volumes

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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 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 volumes at one time. If your system is accessible by an OpenStack cloud, you may see volumes with prefixes indicating that the volumes were created through the OpenStack cloud. Volumes created through the OpenStack cloud use the OpenStack Volume (OSV) and OpenStack Snapshot (OSS) prefixes. Administrative Volumes As part of installation and setup process, a volume called the administrative volume, or admin volume, is created on the system. This volume is used by the system to store administrative data such as the system event log. The admin volume is always named admin. This volume cannot be exported and cannot be removed from the system. CAUTION: It is strongly recommended that you do not tamper with the admin volume. 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). 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 whether 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. 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 one chunklet increments beginning with either 256 MB or 1 GB per controller node. 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. TPVVs are capable of responding to host write requests by allocating space on demand in one chunklet increments beginning with either 256 MB or 1 GB per controller node. These allocations are adaptive since subsequent allocations are based on the rate of consumption for previously allocated space. For example, if a TPVV is initially allocated 256 MB per node but then consumes that space in less than sixty seconds, the next allocation becomes 512 MB per node. However, if the initial 256 MB per node is consumed more slowly, the next allocation increment remains at 256 MB per node. Under this provisioning scheme, the maximum allocation increment is 1 GB per controller node supporting the TPVV. In addition, as the TPVV reaches either its exported size or its user-defined Virtual Volume Types 43

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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 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
volumes at one time.
If your system is accessible by an OpenStack cloud, you may see volumes with prefixes indicating
that the volumes were created through the OpenStack cloud. Volumes created through the OpenStack
cloud use the OpenStack Volume (OSV) and OpenStack Snapshot (OSS) prefixes.
Administrative Volumes
As part of installation and setup process, a volume called the
administrative volume
, or
admin
volume
, is created on the system. This volume is used by the system to store administrative data
such as the system event log. The admin volume is always named
admin
. This volume cannot be
exported and cannot be removed from the system.
CAUTION:
It is strongly recommended that you do not tamper with the admin volume.
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). 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 whether 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.
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 one chunklet increments beginning with either 256 MB
or 1 GB per controller node. 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.
TPVVs are capable of responding to host write requests by allocating space on demand in one
chunklet increments beginning with either 256 MB or 1 GB per controller node. These allocations
are adaptive since subsequent allocations are based on the rate of consumption for previously
allocated space.
For example, if a TPVV is initially allocated 256 MB per node but then consumes that space in
less than sixty seconds, the next allocation becomes 512 MB per node. However, if the initial 256
MB per node is consumed more slowly, the next allocation increment remains at 256 MB per node.
Under this provisioning scheme, the maximum allocation increment is 1 GB per controller node
supporting the TPVV. In addition, as the TPVV reaches either its exported size or its user-defined
Virtual Volume Types
43