Really Interested to hear how you may have got on with this.
We're just about to start something very similar , now on 8.2.4P6 7-mode, on existing deduped vols , although we've never used compression ...in fact believed in inadvisable on 8.1.
On FAS 3240 HA pairs. TWO Cifs volumes on node02, low base CPU c. 10%.
So planning to turn on Post processing compression , not inline, using existing dedupe schedule...just on new data to begin with...
However, if we were to plan compression of each existing volume (3.5TB), the prospect of losing 13 weekly, 72 daily and 6 hourly worth of snaps is not appealing on these user CIFS vols.
Which is 15% full reserve....is not appealing as they get used for restores loads.
Wonder what happens if you proceed to compress leaving all snaps in situ..... or even reduce the set to e.g 8 weeklies ??
So wondering if you deleted all your snaps and went ahead with compressing exising data ...
John