Skip to main content
Hitachi Vantara Knowledge

About parity groups and volumes

Configuring volumes in a parity group

For RAID 5 (7D+1P), RAID 6 (6D+2P), or RAID 6 (14D+2P) a maximum of 2,048 fixed-size volumes (FVs) and a certain amount of free space are available in one parity group. For other RAID levels, a maximum of 1,024 FVs and a certain amount of free space are available in one parity group. Each parity group has the same configuration, and is assigned the same FVs of the same size and RAID level.

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.

Configuration of interleaved parity groups

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.

RAID configuration

2 concatenating

4 concatenating

RAID1 (2D+2D)

Available

Not Available

RAID5 (7D+1P)

Available

Available

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.

NoteEven if the parity groups are concatenated, they cannot be regarded as a large single 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

RAID level support for CVs and pool-VOLs

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

RAID level

RAID configuration that can be applied to CV

RAID configuration that can be applied to pool volume

RAID 1

  • 2D+2D
  • 4D+4D (concatenated 2 parity groups with 2D+2D)
  • 2D+2D
  • 4D+4D (concatenated 2 parity groups with 2D+2D)

RAID 5

  • 2D+1P
  • 3D+1P
  • 4D+1P
  • 5D+1P
  • 6D+1P
  • 7D+1P, or two concatenated 7D+1P parity groups, or four concatenated 7D+1P parity groups
  • 8D+1P
  • 3D+1P
  • 4D+1P
  • 6D+1P
  • 7D+1P, or two concatenated 7D+1P parity groups, or four concatenated 7D+1P parity groups

RAID 6

  • 4D+2P
  • 6D+2P
  • 8D+2P
  • 10D+2P
  • 12D+2P
  • 14D+2P
  • 6D+2P
  • 12D+2P
  • 14D+2P

CV capacity

The following table defines the minimum capacity and maximum capacity for an OPEN-V volume (internal and external).

Emulation type*

Minimum CV capacity

Maximum CV capacity

Number of control cylinders

OPEN-V

48,000 KB (96,000 blocks)

  • Internal volume*: 3,221,159,680 KB (2.99 TB, 6,442,319,360 blocks)
  • External volume: 4,294,967,296 KB (4 TB, 8,589,934,592 blocks)

None

*If the parity group is 2D+1P or 4D+2P, the maximum CV capacity is 2 TB, which is 4,294,967,296 blocks.