Functional comparison of pools and volume groups

The function and purpose of a pool and a volume group are the same. Both objects are a set of drives logically grouped together in a storage array and are used to create volumes that a host can access.

The following table helps you decide whether a pool or volume group best suits your storage needs.
Function Pool Volume Group
Different RAID level supported No. Always RAID 6. Yes. RAID 0, 1, 10, 5, and 6 available.
Thin volumes supported Yes No
Full disk encryption (FDE) supported Yes Yes
Data Assurance (DA) supported Yes Yes
Shelf loss protection supported Yes Yes
Drawer loss protection supported Yes Yes
Mixed drive speeds supported Recommended to be the same, but not required. Slowest drive determines speed for all drives. Recommended to be the same, but not required. Slowest drive determines speed for all drives.
Mixed drive capacity supported Recommended to be the same, but not required. Smallest drive determines capacity for all drives. Recommended to be the same, but not required. Smallest drive determines capacity for all drives.
Minimum number of drives 11 Depends on RAID level. RAID 0 needs 1. RAID 1 or 10 needs 2 (requires an even number). RAID 5 minimum is 3. RAID 6 minimum is 5.
Maximum number of drives Up to the maximum limit for the storage array RAID 1 and 10--up to the maximum limit of the storage array RAID 5, 6--30 drives
Can choose individual drives when creating a volume No Yes
Can specify segment size when creating a volume Yes. 128K supported. Yes
Can specify I/O characteristics when creating a volume No Yes. File system, database, multimedia, and custom supported.
Drive failure protection Uses preservation capacity on each drive in the pool making reconstruction faster. Uses a hot spare drive. Reconstruction is limited by the IOPs of the drive.
Warning when reaching capacity limit Yes. Can set an alert when used capacity reaches a percentage of the maximum capacity. No
Migration to a different storage array supported No. Requires that you migrate to a volume group first. Yes
Dynamic Segment Size (DSS) No Yes
Can change RAID level No Yes
Volume expansion (increase capacity) Yes Yes
Capacity expansion (add capacity) Yes Yes
Capacity reduction Yes No
Note: Mixed drive types (HDD, SSD) are not supported for either pools or volume groups.