topic Re: Deduplication on secondary vol in ONTAP Discussions

Deduplication on secondary vol

deygaurab — Thu, 05 Jun 2025 06:04:12 GMT

Folks,

I have a query on the deduplication. Sorry if it sounds very stupid. I have enabled dedup on all my vmware volumes and they get snapvauled (using smvi) to the secondary.

Do I need to setup dedup on the secondary volumes as well for the primary vmware vols?

Or,

Does the dedup saving of primary volumes get transferred during snapvault replication to the secondary?

Any advise would be greatly apprciated.

Cheers

Rahul

Re: Deduplication on secondary vol

RAVI_PALADUGU — Sun, 28 Apr 2013 05:35:37 GMT

Deduplication and SnapVault

The deduplication feature is integrated with the SnapVault secondary license. This feature increases the efficiency of data backup and improves the use of secondary storage.

The behavior of deduplication with SnapVault is similar to the behavior of deduplication with qtree SnapMirror, with the following exceptions:

Deduplication is also supported on the SnapVault destination volume.
The deduplication schedule depends on the SnapVault update schedule on the destination system. However, the deduplication schedule on the source system does not depend on theSnapVault update schedule, and it can be configured independently on a volume.
Every SnapVault update (baseline or incremental) starts a deduplication process on the destination system after the archival Snapshot copy is taken.
A new Snapshot copy replaces the archival Snapshot copy after deduplication finishes running on the destination system. (The name of this new Snapshot copy is the same as that of the archival copy, but the Snapshot copy uses a new timestamp, which is the creation time.)
You cannot configure the deduplication schedule on the destination system manually or run the sis start command. However, you can run the sis start -s command on the destination system.
The SnapVault update does not depend on the deduplication operation. A subsequent incremental update is allowed to continue while the deduplication operation on the destination volume from the previous backup is still in progress. In this case, the deduplication operation continues; however, the archival Snapshot copy is not replaced after the deduplication operation is complete.
The SnapVault update recognizes the deduplicated blocks as changed blocks. Thus, when deduplication is run on an existing SnapVault source for the first time, all saved space is transferred to the destination system. The size of the transfer might be several times larger than the regular transfers. Running deduplication on the source system periodically will help prevent this issue for future qtree SnapMirror transfers. You should run deduplication before the SnapVault baseline transfer.

Re: Deduplication on secondary vol

deygaurab — Sun, 28 Apr 2013 09:56:19 GMT

Thanks Ravi for a detailed response.

So in short, Once my source volume is setup with dedup, I do not need to configure dedup on the snapvault secondary volume?

Please confirm.

Regards

Rahul

Re: Deduplication on secondary vol

RAVI_PALADUGU — Sun, 28 Apr 2013 14:09:10 GMT

If deduplication is licensed on the snapvault secondary storage system and enabled on the secondary volume, the deduplication process starts automatically after the completion of a snapvault transfer. When you enable deduplication on a existing snapvault secondary volume, the volume may or may not hold replicas of primary data that have never been deduplicated. After a SV update is completed, the newly transferred SV blocks are deduplicated against all of the blocks in the secondary volume.

The deduplication process begins by reviewing the log of changes. The deduplication of blocks is initiated when the number of changed blocks represents at least 20% of the number of blocks in the volume.

Because dedup synchronizes with SV schedule, you cannot schedule the dedup of a SV secondary volume. However you can start the deduplication process manually by using NetApp system manager or the CLI.

Regards,

Re: Deduplication on secondary vol

deygaurab — Mon, 29 Apr 2013 03:43:18 GMT

Thanks Ravi.

Re: Deduplication on secondary vol

deygaurab — Mon, 06 May 2013 13:00:54 GMT

Hello Ravi,

One last query on your point

Does that mean that if I have dedup configured on the primary vol, I cannnot schedule the dedup of a secondary volume? Please let me know

Regards

Rahul D

Re: Deduplication on secondary vol

deygaurab — Mon, 06 May 2013 14:58:42 GMT

I will re phrase my question,

If I want to achive opitimal dedup saving on the secondary volume

1. Considering my primary vol is dedup'ed. Is it mandatory or necessary to schedule the SV update after the dedup has run on the primary? Is there any thumb rule like that?

Thanks in advance for your help.

Re: Deduplication on secondary vol

deygaurab — Mon, 06 May 2013 14:59:12 GMT

If I want to achive opitimal dedup saving on the secondary volume

1. Considering my primary vol is dedup'ed. Is it mandatory or necessary to schedule the SV update after the dedup has run on the primary? Is there any thumb rule like that?

Thanks in advance for your help.

Re: Deduplication on secondary vol

RAVI_PALADUGU — Tue, 07 May 2013 02:25:27 GMT

Hi Rahul,

I think the above explanation was very clear, you wont be scheduling snap vault on secondary volume. ALL YOU NEED TO DO IS ENABLE DEDUP IN SECONDARY VOLUME.

node1> sis on /vol/svprimary

node2> sis on /vol/svsecondary

You can view and accept the default dedup schedule on primary and secondary volumes

node1> sis config /vol/svprimary

node2> sis config /vol/svsecondary

Ravi

Re: Deduplication on secondary vol

deygaurab — Tue, 07 May 2013 03:47:41 GMT

my question was is there any thumb rule to have the dedup run on the parimary prior to an SV update for optimal saving. In my enviromment, there are couple of volumes whose

dedup runs on the primary after the SV update has happened.

Thanks a lot for your help.