HP 3PAR InForm OS 3.1.1 CLI Administrator's Manual

7 Managing CPGs and Virtual Volumes
Overview
A Common Provisioning Group (CPG) creates a virtual pool of logical disks that allows up to 4,095
virtual volumes to share the CPG's resources and allocate space on demand. Virtual volumes draw
their resources from CPGs, and virtual volumes are exported as Logical Unit Numbers (LUNs) to
hosts. Virtual volumes are the only data layer visible to hosts. You can create physical copies or
virtual copy snapshots of virtual volumes for use if the original base volume becomes unavailable.
Before creating virtual volumes, you must first create CPGs to allocate space to the virtual volumes.
The system allows you to create a maximum of 2,048 CPGs on one system. For the maximum
number of virtual volumes that can be created with your specific system configuration, go to the
Single Point of Connectivity Knowledge (SPOCK) website http://spock.corp.hp.com/index.aspx.
For detailed information about CPGs and virtual volumes, see the HP 3PAR InForm OS Concepts
Guide.
For instructions on how to create copies of volumes, see “Managing Virtual Volume Copies”
(page 100).
NOTE: Creating Thinly-Provisioned Virtual Volumes (TPVVs) requires the HP 3PAR Thin Provisioning
Software license. Creating virtual copies or snapshots requires the HP 3PAR Virtual Copy Software
license. Contact your HP representative for more information.
Common Provisioning Groups
By default, a CPG is configured to auto-grow new logical disks when the amount of available
logical disk space falls below a configured threshold. CPGs are initially empty. The initial buffer
pool of logical disks starts off at a fraction of the exported virtual capacity of mapped volumes
and automatically grows over time as required by application writes. For detailed information
about CPG growth warnings and growth limits, see the HP 3PAR InForm OS Concepts Guide.
NOTE: Virtual volumes in the same CPG can share the same logical disk. In the unlikely event
that the logical disk is damaged by multiple simultaneous disk failures, all the volumes associated
with that logical disk will be unavailable.
Growth Increment Considerations for Common Provisioning Groups
The default growth increment of a CPG is fixed at 32 GB, but the minimum growth increment varies
according to the number of controller nodes in the system and ranges from 8 GB for a two-node
system to 32 GB for an eight-node system (Table 8 (page 81)).
Table 8 Default and Minimum Growth Increments
MinimumDefaultNumber of nodes
8 GB32 GB2
16 GB64 GB4
24 GB96 GB6
32 GB128 GB8
There are several courses of action you can take such as adding physical disks to the system, or
limiting the future growth of volumes that draw from the CPG. Your response will vary depending
on several factors:
• Total available space on your system.
• Nature of the data running on the system.
Overview 81