Xsan: Guidelines for volume expansion
When adding storage to an Xsan volume, use these guidelines.
Verify the volume
Always verify the Xsan filesystem’s integrity before and after adding storage to an Xsan volume.
Custom configurations: Bandwidth expansion or storage expansion?
Follow these guidelines if you created your volume using the custom volume type, or if your volume was created using Xsan 1.
A “storage expansion” occurs when LUNs are added to newly created storage pools. When adding capacity to an Xsan volume is the goal, consider storage expansion first.
A “bandwidth expansion” occurs when you add LUNs to existing storage pools. A bandwidth expansion should be considered when the primary goal is to improve the bandwidth of a storage pool. Avoid bandwidth expansions if your goal is only to increase capacity.
Important: Performing a bandwidth expansion on a storage pool that has data on it can result in excessive fragmentation of data on that storage pool. To avoid this, move data on a storage pool that will be expanded to another storage pool or volume before adding LUNs. You can move data back onto the storage pool after bandwidth expansion and it will not be fragmented.
Follow these guidelines if you created your volume in Xsan 2 using one of the preset volume types, such as “General File Server”, “High Definition Video”, and so forth.
If your current volume contains a multiple of the recommended number of LUNs, you should add new LUNs to an affinity tag in multiples of the recommended number. For example, the High Definition Video preset assigns LUNs to storage pools in multiples of 4. If you have a volume created using the High Definition Video preset with 8 LUNs under the “Video” affinity tag, since 8 is a multiple of 4, you can add new LUNs in multiples of 4 to the video affinity tag.
If you want to add LUNs under an affinity tag that does not currently have a multiple of the recommended number of LUNs, you should add a new affinity tag and add LUNs under the new affinity tag in multiples of the recommended number. For example, if you have a volume using the High Definition Video preset with 10 LUNs under the “Video” affinity tag (2 storage pools with 4 LUNs and 1 storage pool with 2 LUNs), since 10 is not a multiple of 4, you should add LUNs to a new affinity tag.
Refer to the Xsan 2 Administrator's Guide for more information on expanding an Xsan volume and the recommended multiple of LUNs for each volume preset type.