You can create volumes using either a pool or a volume group. The best selection depends primarily on the key storage requirements such as the expected I/O workload, the performance requirements, and the data protection requirements.
Choose a pool
If you need faster drive rebuilds and simplified storage administration, require thin volumes, and/or have a highly random workload.
If you want to distribute the data for each volume randomly across a set of drives that comprise the pool.
You cannot set or change the RAID level of pools or the volumes in the pools. Pools use RAID level 6.
Choose a volume group
If you need maximum system bandwidth, the ability to tune storage settings, and a highly sequential workload.
If you want to distribute the data across the drives based on a RAID level. You can specify the RAID level when you create the volume group.
If you want to write the data for each volume sequentially across the set of drives that comprise the volume group.
The following table provides a feature comparison between volume groups and pools.
| Use | Pool | Volume group |
|---|---|---|
| Workload random | Better | Good |
| Workload sequential | Good | Better |
| Drive rebuild time | Faster | Slower |
| Performance (optimal mode) | Good: Best for small block, random workload. | Good: Best for large block, sequential workloads |
| Performance (drive rebuild mode) | Better: Usually better than RAID 6 | Degraded: Up to 40% drop in performance |
| Multiple drive failures | Greater data protection: Faster, prioritized rebuilds | Less data protection: Slow rebuilds, greater risk of data loss |
| Adding drives | Faster: Add to pool on the fly | Slower: Requires Dynamic Capacity Shelf operation |
| Thin volumes support | Yes | No |
| Solid State Disk (SSD) support | Yes | Yes |
| Simplified administration | Yes: No hot spares or RAID settings to configure | No: Must allocate hot spares, configure RAID |
| Tunable performance | No | Yes |