Need to know the difference between storage pool and RAID group?

Feature

Thick LUN

Thin LUN

RAID Group LUN

Pool RAID types

RAID 6, RAID 5, or RAID 1/O.

RAID 6, RAID 5, or RAID 1/O.

RAID 6, RAID 5, RAID 3, RAID 1/0, or RAID 1 RAID groups, individual disk, or hot spare.

LUN expansion

Fully supported.

Fully supported.

Only supported using metaLUNs.

LUN shrinking

Fully supported for Windows Server 2008 hosts.

Fully supported for Windows Server 2008 hosts.

Fully supported for Windows Server 2008 hosts connected to a storage system running R30 or later for pool LUNs (thin and thick) and R29 for RAID group LUNs.

LUN compression

Fully supported if the Compression enabler is installed.

Fully supported if the Compression enabler is installed.

Supported if the Compression enabler is installed, but migrates the RAID group LUN to a pool LUN.

LUN migration

Fully supported.

Fully supported.

Fully supported.

Disk usages

Any type of disk, including Flash (SSD) disks, can be in the pool with the thick LUN. The disks in the pool with the thick LUN cannot be the vault disks 000–004.

Any type of disk, including Flash (SSD) disks, can be in the pool with the thin LUN. The disks in the pool with the thin LUN cannot be the vault disks 000–004.

All disks in the RAID group with the LUN must be of the same type.

Space efficiency

When you create a thick LUN, the LUN is assigned physical space on the pool equal to the LUN’s size. This space is always available to the LUN even if it does not actually use the space.

When you create a thin LUN, a minimum of 2 GB of space on the pool is reserved for the thin LUN. Space is assigned to the thin LUN on an as-needed basis. Since the thin LUNs compete for the pool’s space, a pool can run out of space for its thin LUNs. Such an event is an unrecoverable write error and data from the last write operation will not be available. Some applications, such as VERITAS Storage Foundation, may return space no longer needed to the pool by an appropriate signaling to the storage system.

When you create a LUN, the LUN is assigned physical space on the RAID group equal to the LUN’s size. This space is always available to the LUN even if it does not actually use the space.

Performance

Thick LUN performance is comparable to the performance of a RAID group LUN and is typically faster than the performance of a thin LUN.

Thin LUN performance is typically slower than thick LUN performance.

RAID group LUN performance is comparable to the performance of a thick LUN and is typically faster than thin LUN performance.

Manual administration

Pools require less manual administration than RAID groups.

Pools require less manual administration than RAID groups.

RAID groups require more manual administration than pools.

Use with SnapView

Fully supported for thick LUNs. A thick LUN cannot be a clone private LUN.

A thin LUN can be a snapshot source LUN, a clone LUN, a clone source LUN, but not a clone private LUN, and not in the reserved LUN pool. A thin LUN cannot be a clone private LUN.

Fully supported for RAID group LUNs.

Use with MirrorView/A or MirrorView/S

Fully supported for thick LUNs. A thick LUN cannot be used in the write intent log.

Mirroring with thin LUNs as primary or secondary images is supported only between storage systems running FLARE 04.30 or later. For mirroring between storage systems running FLARE 04.30, the primary image, secondary image, or both images can be thin LUNs. A thin LUN cannot be used in the write intent log.

Fully supported for RAID group LUNs.

Use with SAN Copy

Fully supported for thick LUNs in all configurations.

Thin LUNs are supported only for SAN Copy sessions in the following configurations:1)Within a storage system running FLARE 04.30 or later, 2)Between systems running FLARE 04.30 or later The source LUN must be on the storage system that owns the SAN Copy session.

Fully supported for RAID group LUNs in all configurations.