Pool-VOL requirements

Pool-VOLs make up a DP pool.

Item

Requirements

Volume type

Logical volume (LDEV)

While pool-VOLs can coexist with other volumes in the same parity group, for best performance:

  • Pool-VOLs for a pool should not share a parity group with other volumes.
  • Pool-VOLs should not be located on concatenated parity groups.

Pool-VOLs cannot be used for any other purpose. For instance, you cannot specify the following volumes as pool-VOLs:

  • Volumes used by ShadowImage, Volume Migration, TrueCopy, global-active device, or Universal Replicator
  • Volumes already registered in Thin Image, Dynamic Provisioning, Dynamic Provisioning or active flash pools
  • Volumes used as Thin Image P-VOLs or S-VOLs
  • Volumes reserved by Data Retention Utility
  • Data Retention Utility volumes with a Protect, Read Only, or S-VOL Disable attribute
  • LDEVs whose status is other than Normal, Correction Access, or Copying. You cannot specify volumes in blocked status or volumes in copying process.
  • Command devices
  • Quorum disks used by global-active device

The following volume cannot be specified as a pool-VOL for Dynamic Tiering:

  • An external volume with the data direct mapping attribute enabled.

If pool-VOLs are LDEVs created from the parity group with accelerated compression enabled, these pool-VOLs must be applied to one pool.

Emulation type

OPEN-V

RAID level for a Dynamic Provisioning pool

You can use one of the following RAID levels:

  • RAID 1 (2D+2D, or concatenated 2 of 2D+2D)
  • RAID 5 (3D+1P, 4D+1P, 6D+1P, 7D+1P, concatenated 2 of 7D+1P, or concatenated 4 of 7D+1P)
  • RAID 6 (6D+2P, 12D+2P, or 14D+2P)

Pool-VOLs of RAID 5, RAID 6, RAID 1, and external volumes can coexist in the same pool. For pool-VOLs in the same pool:

  • RAID 6 is the recommended RAID level for pool-VOLs, especially for a pool where the recovery time of a pool failure due to a drive failure is not acceptable.
  • Pool-VOLs of the same drive type with different RAID levels can coexist in the same pool. We recommend that you set one RAID level for pool-VOLs. If you register pool-VOLs with multiple RAID levels to the same pool, the I/O performance depends on the RAID levels of pool-VOLs to be registered. In that case, note the I/O performance of the drives.

RAID level for a Dynamic Tiering or active flash pool

You can use one of the following RAID levels:

  • RAID 1 (2D+2D, or concatenated 2 of 2D+2D)
  • RAID 5 (3D+1P, 4D+1P, 6D+1P, 7D+1P, concatenated 2 of 7D+1P, or concatenated 4 of 7D+1P)
  • RAID 6 (6D+2P, 12D+2P, or 14D+2P)

Pool-VOLs of RAID 5, RAID 6, RAID 1, and external volumes can coexist in the same pool. For pool-VOLs in the same pool:

  • RAID 6 is the recommended RAID level for pool-VOLs, especially for a pool where the recovery time of a pool failure due to a drive failure is not acceptable.
  • Pool-VOLs of the same drive type with different RAID levels can coexist in the same pool. Set one RAID level for pool-VOLs. If you register pool-VOLs with multiple RAID levels to the same pool, the I/O performance depends on the RAID levels of pool-VOLs to be registered. In that case, note the I/O performance of the drives.
  • Because the speed of RAID 6 is slower than other RAID levels, tiers that use other RAID levels should not be placed under a tier that uses RAID 6.

Data drive type for a Dynamic Provisioning pool

SSD, SAS15K, SAS10K, SAS7.2K, FMD DC2, and external volumes can be used as the data drive type. These data drive types can coexist in the same pool.

Cautions:

  • Best practice is for drives of different types not to coexist in the same pool. If multiple pool-VOLs with different drive types are registered in the same pool, the I/O performance depends on the drive type of the pool-VOL to which the page is assigned. Therefore, if different drive types are registered in the same pool, ensure that the required I/O performance is not degraded by using less desirable drive types.
  • If multiple data drives coexist in the same pool, we recommend not using data drives that are the same types and different capacities.

Data drive type for a Dynamic Tiering or active flash pool

SSD, SAS15K, SAS10K, SAS7.2K, FMD DC2, and external volumes can be used as the data drive type. These data drive types can coexist in the same pool. If active flash is used, SSD, FMD DC2, drives must be installed in advance.

Caution: If multiple data drives coexist in the same pool, we recommend not using data drives that are the same types and different capacity sizes.

Volume capacity

Internal volume: From 8 GB to 2.9 TB

External volume: From 8 GB to 4 TB

External volume with the data direct mapping attribute: From 8 GB to 256 TB

LDEV format

The LDEV format operation can be performed on pool-VOLs only when all of the following conditions are satisfied:

  • There are no DP-VOLs defined for the pool, or all DP-VOLs defined for the pool are blocked.
  • The pool does not contain any Thin Image pairs or snapshot data.

Path definition

You cannot specify a volume with a path definition as a pool-VOL.

Parent Topic