A Note on Defragmentation

Do not defragment volumes on an array. The value of defragmentation is mainly on a local physical disk to keep files contiguous so the disk heads do not require unnecessary physical seeks across the platters, and slow down file I/O.

There is no such value about the effectiveness of this in a networked iSCSI environment, especially where files are stored on storage devices that have their own layers of virtualization.

Defragmenting files in a storage array environment results in changed blocks, even though the files did not change, and can have unnecessary impacts, such as snapshots being larger than they should.