Functional comparison of pools and volume groups
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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 |
|
Mixed drive types (HDD, SSD) are not supported for either pools or volume groups. |