I wonder if anyone can help? I've been doing a bit of reading up on the potential for space savings if I switch on deduplication on a SnapVault target.
The source volume is question is mainly Microsft Office type documents and would therefore benefit greatly from SIS. Actually, we do dedupe the source volume but as I understand it, any benefit is lost in the snapvaulting process.
Most of the advise recommends that SIS is enable prior to the first snapshot being taken. Unfortunately we've missed the boat on this and the peculiar nature of this volume means we retains snapvault snapshots up to one year old.
Can anyone confirm that:
a) We can retrospecitively enable SIS on the SnapVault destination.
b) How long will it be before we start to see a benefit (I suspect we won't see anything until the older snapshots begin to expire).
c) How much free space am I likely to need to perform this? Am I likely to see much growth in the volume during the SIS START process? The snapvault target volume is 3TB in size with 2.5TB in use (about 1.5TB is current data and 1TB is SV snapshots.)
Did you ever get an answer to this question? You've described the exact same question I was going to post.
We have dedupe enabled at the source but not at the destination. I have enabled dedupe and forced a manual scan but all it seems to have done is placed all of the potential savings in to a 400gb snap which I guess will be there for another 12 months now!
I've also noticed that there is any way to set the storage efficiency to be automatic, even after the dedupe completes. I'm finding it difficult to get a clear answer on this!
b) Your suspicion is correct. You will only start to see big benefits once all pre-dedup snapshots have expired.
c) Difficult to say. You will really need the extra space for the big snapshot(s) until the pre-dedup snapshots expire. Once you've got a couple of snapshots going on the destination volume, you will have dedup benefits on those snapshots, but they will not compensate for the pre-dedup snapshots.
I am not quite sure what you mean by that last comment about storage efficiency. On a SnapVault destination with dedup enabled, you will get automatic dedup runs after SV updates. Doesn't that qualify "storage efficiency to be automatic" ?
In regards to your comment about Storage Efficiency only being able to be set as Manual. Are you referring to within the OnCommand interface? I am looking at enabling Deduplication on our Snapvault volumes as well and was curious about this step. Does it list in OnCommand as Manual and then kick off a dedupe run after a SV update but it still shows as Manual within the OnCommand interface?
I have come across the same situation as well. I have read these documents related to snapvault and dedupe'. It seems safe to me and as "uptime" stated above in his comments in summary has hit the nail on the head.