HP 3PAR InForm OS 3.1.1 Concepts Guide

Growth Increment
As volumes that draw from a CPG require additional storage, the system automatically creates
additional logical disks according to the CPG's growth increment. The default growth increment
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 a four-node system
(Table 5 (page 41)).
Table 5 Default and Minimum Growth Increments
MinimumDefaultNumber of nodes
8 GB32 GB2
16 GB32 GB4
24 GB32 GB6
32 GB32 GB8
In some it may be desirable to use a larger growth increment. However, a smaller growth increment
can prevent the CPG from automatically allocating too much space.
The optimal growth increment depends on several factors:
• Total available space on your system.
• Nature of the data running on the system.
• Number of CPGs in the system.
• Number of volumes associated with those CPGs.
• Anticipated growth rate of the volumes associated with the CPGs.
NOTE: The system may round up when creating logical disks to support virtual volumes and
Common Provisioning Groups (CPGs), resulting in a discrepancy between the user-specified size
or growth increment and the actual space allocated to logical disks created by the system. For a
detailed discussion of this issue, see “Logical Disk Size and RAID Types” (page 39).
Growth Warning
When the size of the volumes that draw from a CPG reach the CPG’s growth warning, the system
generates an alert to notify you of the CPG's increasing size. This safety mechanism provides the
opportunity to take early action that may prevent snapshot volumes associated with the CPG from
experiencing failures, causing host or application write failures, and exhausting all free space on
the system.
When setting growth warnings for CPGs, it is critical to consider the number of CPGs on the system,
the total capacity of the system, and the projected rate of growth for all volumes on the system.
The storage system does not prevent you from setting growth warnings that exceed the total capacity
of the system. For example, on a 3 TB system you can create two CPGs that each have a growth
warning of 2 TB. However, if both CPGs grow at a similar rate, it is possible for the volumes that
draw from the CPGs to consume all free space on the system before either CPG reaches the growth
warning threshold.
Growth Limit
If the volumes that draw from a CPG are allowed to reach the CPG’s growth limit, the system
prevents them from allocating additional space. This safety mechanism stops a runaway application
or volume from exhausting all free space available to the CPG and causing invalid (stale) snapshot
volumes and/or new application write failures for volumes associated with that CPG. However,
the storage system does not prevent you from setting growth limits that exceed the total capacity
Precautions and Planning 41