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

Table 4 Default and Minimum Growth Increments
MinimumDefaultNumber of nodes
8 GB32 GB2
16 GB64 GB4
24 GB96 GB6
32 GB128 GB8
A larger growth increment is sometimes desirable; 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 LDs are created to support virtual volumes and CPGs,
resulting in a discrepancy between the user-specified size or growth increment and the actual
space allocated to LDs created by the system. For a detailed discussion of this issue, see “LD Size
and RAID Types” (page 40).
Growth Warning
When the size of the volumes that draw from a CPG reach the CPG growth warning, the system
generates an alert. 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 you set 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 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 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 of
the system. For example, on a 4 TB system it is possible to create a CPG with a 5 TB growth limit.
Likewise, it is possible to create five CPGs, each with a 2 TB growth limit.
In addition, volumes that draw from a CPG can use only the space available to that CPG based
on the CPG LD parameters. For example, if you create a CPG that only uses LDs that belong to
42 Common Provisioning Groups