3PAR InForm® OS 2.3.1 Concepts Guide (320-200112 Rev B, February 2010)

9.4
Precautions and Planning
3PAR InForm OS Concepts Guide InForm OS Version 2.3.1
9.2.2 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 9-1).
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.
Table 9-1. Default and Minimum Growth Increments
Number of nodes Default Minimum
2 32 GB 8 GB
4 32 GB 16 GB
6 32 GB 24 GB
8 32 GB 32 GB
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 on page 8.8.