volume shrink

In Longhorn it will be possible (at least it is possible in build 5718) to shrink volumes. I tried this in a Virtual Server installed Longhorn and it worked like a charm. I do not know Why the amount of space available for shrinking is this size: the disk is filled with about 6GB of “data” It may have something to do with the location of data ever written to this disk. 

Sounds as useful as the extend volume option: Darn, I made a mistake, throw away the volume: yeah right.. and lose my data?