HP 3PAR StoreServ 7450 4-node HP 3PAR StoreServ Storage Concepts Guide (OS 3.1 - Page 41
System Guidelines for Creating CPGs, Volume Types Associated with CPGs, Logical
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In addition, volumes that draw from a CPG can only use the space available to that CPG based on the CPG's logical disk parameters. For example, if you create a CPG that only uses logical disks that belong to controller node 0, when the virtual volumes that draw from a CPG have filled up all space available to that CPG based on it's logical disk parameters, the following will happen: • New writes to any TPVVs mapped to that CPG will return write failures. • Snapshot volumes mapped to the CPG may become invalid (stale), subject to the virtual copy policy associated with the base volume. For base volumes with a no stale snapshots virtual copy policy, new writes to the base volume will result in write failures. • 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. 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 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" (page 38). Volume Types Associated with CPGs Depending on the products and features licensed for use on the system, after creating a CPG you can create two types of base volumes that draw from the CPG's logical disk pool: Thinly Provisioned Virtual Volumes (TPVVs) and fully provisioned virtual volumes. These two volume types draw from the pool in different ways. For information about TPVVs, see "Thinly-provisioned Virtual Volumes" (page 8). For information about fully provisioned virtual volumes, see "Fully-provisioned Virtual Volumes" (page 8). System Guidelines for Creating CPGs 41