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SANtricity 11.5
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Decide whether to use a pool or a volume group

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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.

Reasons to choose a pool or volume group

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.

Note

Because pools can co-exist with volume groups, a storage array can contain both pools and volume groups.

Feature differences between pools and volume groups

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 Expansion 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