Data ONTAP Discussions

Why should we disable dedupe when using Protection Manager?


I have a question regarding the documents on NOW:

Backup und Debup


Do not use Protection Manager 3.7 on volumes that have deduplication enabled.


Okay, I know OM 3.7 is not aware of Dedupe. But it is still possible to do backups with dedupe enabled on the primary side.

My Customer found this and is asking if this also applies for the PM in 3.8 Version.

Additional question is...

Do we need Provisioning Manager license for future Protection Manager installs, if we want to use dedupe on primary and secondary snapvault relationship? (got something in my mind from talking with PMs)


Re: Why should we disable dedupe when using Protection Manager?

I think the only rationale behind that recommendation (I'd treat that as a recommendation) is explained on that page:

if snapshots exist, de-dupe will 'release' duplicate blocks & the youngest (if my memory servers OK) snapshot will be grown by exactly the same size as de-dupe 'saving'.

But this issue is not specific by any means to just Protection Manager.



Re: Why should we disable dedupe when using Protection Manager?

I'm sure I've heard that de-dupe is much improved for Snapshots in DOT 7.3.2 (which we're running). Does this mean that this recommendation/limitation no longer applies?

We're also runnuing DFM 3.8.


Re: Why should we disable dedupe when using Protection Manager?


I think you will find that Dedupe has just changed the way in which it stores it database and not improved on how it does the actual post process work.

Snapshots are still a major factor when deduping volumes.

You may want to reference this thread.


Re: Why should we disable dedupe when using Protection Manager?

Thanks for the reply Anthony.

If I read the other thread correctly I should be able to have regular (daily) snapshots  and keep using de-dupe by ensuring I have them scheduled in the right order?

Page 20 says:

For deduplication to provide themost benefit when used in conjunction with Snapshot copies, the following bestpractices should be considered:

·         Run deduplication before creating new Snapshot copies.

·         Remove unnecessarySnapshot copies maintained in deduplicated volumes.

·         If possible, reduce the retention time of Snapshot copies maintained in deduplicated volumes.

·         Schedule deduplication only after significant new data has been written to the volume.

But then again I've also read that you only need to de-dupe the initial baseline since Snapavault in DOT 7.3 integreates de-dupe and it is automatically performed when the snapvault backup has completed. Is this correct?

Also what's the best policy with regards to adding new snapvault primaries to a secondary volume? For example, I have a volume on the secondary used to hold the snapshots of C: drives from a number of OSSV clients. In a few weeks time a new Wintel server comes online and I want to integrate it in to the existing volume to use the current schedules, etc... After performing the baseline of the new system should I do a manual sis start -s or, by contrast, should new systems go in to a new volume?