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

9.6
System Guidelines for Creating CPGs
3PAR InForm OS Concepts Guide InForm OS Version 2.3.1
■ For base volumes with a stale snapshots virtual copy policy, new writes will cause
snapshot volumes to become invalid (stale).
■ If the volumes that draw from a CPG reach the CPG’s growth limit, the system generates
additional alerts to notify you that all logical capacity for the CPG has been consumed.
9.3 System Guidelines for Creating CPGs
Use the following guidelines to ensure maximum performance and optimal reliability in the
volumes supported by those logical disks:
■ To provide the highest availability, chunklets in the same RAID set should be from different
drive cages, and then different drive magazines.
■ Physical disks with fewer used chunklets should be used before physical disks with more
used chunklets.
■ Chunklets in the same row should be from different physical disks. In other words, a
physical disk should not appear twice in the same row.
■ Chunklets should belong to a disk that is connected through the primary path to the logical
disk’s owner node.
■ The system should use as many physical disks as possible.
■ The load on all physical disks should be balanced.
■ The system should use the largest possible row size.
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 more information, see Logical
Disk Size and RAID Types on page 8.8.