HP 3PAR Operating System Software - Manual (Page 109)

When volumes draw additional space from the CPG, the volumes
become larger and require additional storage space.
To expand a volume’s storage space, the system automatically creates
additional logical disks and adds them to the CPG.
This expansion continues as necessary until the CPG reaches its
specified allocation limit.
The system cannot allocate space on demand to FPVVs. The system
can only allocate space on demand to snapshots of these volumes. FPVVs
Basic Information about CPGs
NOTE: For a complete list of warnings and cautions regarding CPGs, see the HP 3PAR StoreServ
Storage Concepts Guide.
A CPG creates a virtual pool of logical disks that allows volumes to share the CPG's resources and
allocate space on demand. However, CPGs still require careful planning and monitoring to prevent
them from becoming too large. The maximum number of CPGs per system is 2,048.
Built-in safety mechanisms are designed to prevent a CPG from consuming all free space on the
system, but they work properly only on systems that are planned carefully and monitored closely.
Creating a CPG
To create a CPG, see the HP 3PAR Command Line Interface Administrator’s Manual.
Virtual Volumes Used with Remote Copy
Two types of virtual volumes can be used with remote copy. These virtual volumes draw different
amounts of space from the CPG with which they are associated.
CPG Space Allocated Type of Virtual Volume
All data and snapshot space is allocated on demand from the CPG. TPVVs
Only snapshot space is allocated on demand from the CPG. FPVVs
Thinly-Provisioned Virtual Volumes
A thinly-provisioned virtual volume (TPVV) draws space as necessary from the CPG with which it
is associated. The CPG allocates space on demand in small increments.
By default, TPVVs do not have snapshot space. To use TPVVs with remote copy, you must create
TPVVs with snapshot space.
When you perform the initial synchronization of a TPVV that is configured as a primary remote-copy
virtual volume, HP 3PAR Remote Copy sends only the allocated data pages to the secondary virtual
volume on the backup system.
When you configure a TPVV as a primary virtual volume in a remote-copy volume group, you must
make sure that either the secondary virtual volume has no data written to it before you add it to
the remote-copy volume group, or that it matches the primary volume.
For more information about creating a TPVV, see the HP 3PAR Command Line Interface
Administrator's Manual.
Fully Provisioned Virtual Volumes
FPVVs only draw snapshot space from the CPG.
For more information about creating an FPVV, see the HP 3PAR Command Line Interface
Administrator's Manual.
Virtual Volumes and CPGs 109