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 in System Manager. | 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.
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