Correct.  If you already have a directory quota that you are using to enforce or monitor space usage, add a second quota that monitors usage + snapshots.  Then you can subtract the 2 numbers and get the amount of snapshot space used in that part of the directory tree.
hello,   is there any way i can find out snapshot space usage of single share ? i can see the total space of all on isilon snapshot tab but i am looking for single share basically we are analyzing how much of specific shares are taking that way we want to increase the number of shapshots and retentions. we have insightiq as well but i couldn't find any reporting stuff of snapshots in insightIQ.  appreciate any help on this.
snapshot usage report of specific share