A-SIS SnapVault destination question

Real quick one,

Do you turn on dedup before you do the initial transfer or after?

Re: A-SIS SnapVault destination question


Run SIS and make sure its done BEFORE any snaps are taken to get the gains straight away and to propagate them to SM and/or SV destinations.

If you have ie 6 daily snaps in your volume at the time of turning SIS on you wont see the full gains until they have rotated out of the volume.

I keep a schedule of what SM and SV jobs we run per controller and make sure all my SIS jobs are finished before SM/SV kicks in.


edited: I forgot to say that from 7.3.2 snapvault and SIS are integrated so that SIS is automatically run on a destination when updated. this is

off the top of my head so doublecheck.

From the VERY fresh FAQ that was released just now:


Yes. NetApp deduplication is supported on SnapVault volumes in the 7.3 or higher


The answer is yes, but there are differences between implementations of Volume SnapMirror (VSM) and Qtree SnapMirror (QSM):

With VSM, deduplication is performed only on the source volume. Since the source volume is replicated block-for-block to the VSM destination volume, this results in deduplication space savings at the source and the destination, as well as reduced bandwidth during the replication data transfer. A NearStore license and deduplication license is required on both the source and destination VSM volumes.

With QSM, deduplication can be enabled at the source volume, the destination volume, or both the source and destination volumes. If the QSM source volume is deduplicated, you will not see any bandwidth savings, and the volume will be "un-deduplicated" as it is

NetApp Deduplication FAQ 8/25/2008 Page 11 of 12

stored at the destination. To deduplicate the destination, deduplication would need to be run on that volume after the QSM data transfer.

Re: A-SIS SnapVault destination question

Thanks Eric,

So the procedure for a volume with daily vaults taken at 11PM retaining 30, would be:

  1. snapvault start -S primary:/vol/vol/qtree secondary:/vol/vault/qtree
  2. sis on /vol/vault
  3. sis start -s /vol/vault
  4. snapvault snap sched -x /vol/vault/qtree sv_daily 30@23

Is this correct? or do I sis on /vol/vault/qtree before kicking off the snapvault initial?

Re: A-SIS SnapVault destination question

Hi again,

Finish SIS off BEFORE anything that involves a snapshot starts. The reason is that if you do a snap first and then a SIS you wont get the gains from SIS

until the snap is gone. This is because snaps are read only and thus SIS cant wrote to those blocks. So SIS first then snaps.