HP 3PAR StoreServ Concepts Guide: HP 3PAR OS 3.1.3

8 Common Provisioning Groups
Overview
A CPG creates a virtual pool of LDs that allows virtual volumes to share the CPG's resources and
allocates space on demand. You can create FPVVs and TPVVs that draw space from the CPG's
LD pool.
CPGs enable fine-grained, shared access to pooled logical capacity. Instead of dedicating LDs to
volumes, the CPG allows multiple volumes to share the buffer pool of LDs. For example, when a
TPVV is running low on user space, the system automatically assigns more capacity to the TPVV
by mapping new regions from LDs in the CPG associated with that TPVV. As a result, any large
pockets of unused but allocated space are eliminated. FPVVs cannot create user space automatically,
and the system allocates a fixed amount of user space for the volume.
By default, a CPG is configured to grow new LDs automatically when the amount of available LD
space falls below a configured threshold. The initial buffer pool of LDs starts at a fraction of the
exported virtual capacity of mapped volumes and automatically grows as required by application
writes.
CPGs can be created by using both the HP 3PAR CLI and the HP 3PAR Management Console.
See the HP 3PAR Command Line Interface Administrator’s Manual and the HP 3PAR Management
Console Online Help for instructions on performing these tasks.
For more information about TPVVs and FPVVs, see “Virtual Volumes” (page 44).
Precautions and Planning
A CPG creates a virtual pool of LDs that allows up to 4,095 volumes to share the CPG resources
and allocate space on demand. The maximum number of CPGs per system is 2,048.
Growth Increments, Warnings, and Limits
You can create several types of volumes that draw space from the CPG LD pool. When creating
a CPG, set a growth increment and an optional growth warning and growth limit to restrict the
CPG growth and maximum size. It is important to plan the CPG growth increment, growth warning,
and growth limit carefully and then continue to monitor the CPG closely over time.
CAUTION: Use caution in planning CPGs. The system does not prevent you from setting growth
warnings or growth limits that exceed the amount of currently available storage on a system. When
volumes associated with a CPG use all space available to that CPG, any new writes to TPVVs
associated with the CPG will fail and snapshot volumes associated with the CPG may become
invalid or stale. Under these conditions, some host applications do not handle write failures
gracefully and may produce unexpected failures.
NOTE: By default, the growth warning and growth limit are set to none, which effectively disables
these safety features.
Growth Increment
As volumes that draw from a CPG require additional storage, the system automatically creates
additional LDs according to the CPG growth increment. The default and minimum growth increments
vary according to the number of controller nodes in the system, as shown in Table 4 (page 42).
Overview 41