You enable logical extents for volumes that contain Microsoft Exchange data only. The decision to use logical extents involves a trade-off between improved database validation performance and runtime performance. Use logical extents when you want to improve validation performance. If runtime performance is higher priority, you might not want to use extents.
Using logical extents also causes the active file system of the volume to diverge more quickly from any Snapshot copies in the volume. This can result in greater space requirements for the volume, depending on the Snapshot copy schedule and rate of updates to the volume.
Similarly, SnapMirror updates may transfer more information since additional blocks are updated. This difference may range from negligible to up to three times the updated block count.
Finally, using logical extents increases write latency under heavy I/O.