About parity groups and volumes

The Delete LDEV and Create LDEV functions are performed on each parity group. Parity groups are also separated from each other by boundary limitations. Therefore, you cannot define a volume across two or more parity groups beyond these boundaries.

As the result of creating and deleting LDEVs, a parity group contains CVs and free spaces that are delimited in logical cylinders. Sequential free spaces are combined into a single free space.

If RAID configurations are RAID1 (2D+2D) or RAID5 (7D+1P), the interleaved parity group can be created by concatenating multiple of parity groups. The following table lists the RAID configurations and the number of parity groups that can be concatenated.

When concatenating parity groups, data in LDEVs is allocated between the interleaved parity groups. Therefore, loads are dispersed because of the parity group concatenation, and the LDEV performance is improved.

The capacity of the created LDEV is managed by each of the parity groups that are in the interleaved parity group. The maximum capacity of an LDEV is the same as the capacity of the interleaved parity group.

See the following example:

• Creating the interleaved parity group by concatenating parity groups PG1-1 and PG1-2.
• Creating LDEVs in each parity group that are in the interleaved parity group.
  • LDEV 1 in PG1-1
  • LDEV 2 in PG1-2

The following table specifies the RAID level support for custom volumes (CVs) and pool volumes (pool-VOLs).

Create normal (thick) volumes