HP 3PAR Remote Copy Software - Manual (Page 50)

2.34 Remote Copy and Thin Provisioning
Remote Copy User’s Guide InForm OS Version 2.3.1
For example, when Remote Copy requires that the system create a new snapshot of a volume,
the volume’s CPG might need to allocate additional space to that volume. That space is drawn
from the system’s common storage pool, at which point it is placed into the CPG’s individual
pool and then allocated to the volume. After the resynchronization takes place and the
snapshot is no longer useful, Remote Copy deletes the snapshot from the system. At that time,
the space formerly allocated for that snapshot is returned to the volume’s free space.
Contiguous free snapshot data space can be reclaimed and returned to the CPG using
3PAR Thin Copy Reclamation. Refer to the InForm OS Concepts Guide for information about
3PAR Thin Copy Reclamation.
2.12.2 Thinly Provisioned Virtual Volumes
Thinly Provisioned Virtual Volumes (TPVVs) associated with the same CPG, draw space from
that pool as necessary, by allocating space on demand in small increments. As the volumes that
draw 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 allocation limit
that restricts its maximum size.
Before creating a TPVV, you must first create a CPG as described in the 3PAR InForm OS CLI
Administrator’s Manual. After the CPG is established, use the instructions in the 3PAR InForm
OS CLI Administrator’s Manual to create volumes that draw from that pool.
NOTE: While it is possible for a CPG to have up to 4095 volumes, it is strongly
recommended that no more than 32 volumes be associated with a single CPG. The
reasons for this limit are as follows:
■ Virtual volumes in the same CPG can share the same logical disk. In the unlikely
event that the logical disk is damaged (because of multiple simultaneous disk
failures, for example), all the volumes associated with that logical disk will be
unavailable.
■ Virtual volume performance might suffer from too much interleaving within the
logical disks.
NOTE: Thinly Provisioned Virtual Volumes (TPVVs) do not have snapshot space by
default. In order to use TPVVs with Remote Copy., you must create TPVVs with
snapshot space.