NetApp: SnapMirror RPO

We use Async SnapMirror at 3 hour intervals primarily to allow larger change volumes to finish replication, and not have competition from other snapmirror volumes.

Recently, we fixed an issue on our network which more than doubled our bandwidth.

All SnapMirror volumes replicate in less than an hour on average. We are now seeking a better RPO.

How do we decide what a good RPO is?
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pzozulkaAsked:
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Paul SolovyovskySenior IT AdvisorCommented:
Do a "snap delta" and see how long it takes to replicate changes.
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pzozulkaAuthor Commented:
Not sure which statistic too look at. Here are the results of an average volume look like:

From Snapshot   To                   KB changed  Time         Rate (KB/hour)
--------------- -------------------- ----------- ------------ ---------------
i1lvnapp01_vol3.3145 Active File System   998596         0d 01:12  827375.281
hourly.0       _vol3.3145 1285108        0d 01:29  860883.662
nightly.0       hourly.0             7536108        0d 07:59  942275.243
hourly.1        nightly.0            4856432        0d 04:00  1213602.332
nightly.1       hourly.1             11904596       0d 19:59  595320.751

Summary...

From Snapshot   To                   KB changed  Time         Rate (KB/hour)
--------------- -------------------- ----------- ------------ ---------------
nightly.1       Active File System   26580840       1d 10:41  766104.302

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pzozulkaAuthor Commented:
The largest volume we have is:

Summary...

From Snapshot   To                   KB changed  Time         Rate (KB/hour)
--------------- -------------------- ----------- ------------ ---------------
nightly.1       Active File System   60564608       1d 10:42  1745140.261

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Paul SolovyovskySenior IT AdvisorCommented:
Actually snapmirror status may be a better command, or better yet download

Snapmirror Progress Monitor from the tools on the Netapp site.  This will give you a good idea of how much data is replication and how long it takes.

Another option to reduce RPO is to enable snapmirror compression, this does use CPU cycles at the source or use a WAN accelerator like Riverbed (which can be installed as a VM or physical)
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pzozulkaAuthor Commented:
For the largest change volume mentioned above:

snapmirror status -l i1lvnetapp01:i1lvnapp02_vol4

Last Transfer Size:     3965752 KB
Last Transfer Duration: 01:35:25

We have compression enabled on all snapmirror vols.
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Paul SolovyovskySenior IT AdvisorCommented:
So your RPO is under 4 hours I would say (this gives you buffer for growth).  What type of data are you replicating?
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pzozulkaAuthor Commented:
Everything from Exchange to SQL databases, user profiles, web servers. Just the usual business applications.

Would you say an RPO of 2 hours justified?
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Paul SolovyovskySenior IT AdvisorCommented:
I wouldn't do less than 3 hours as your data may grow and thus a new RPO established.  Give yourself  buffer for network interruptions, larger than normal snapshots, etc..

I would also recommend using vfilers for CIFS/NFS, otherwise you would need to re-create shares at the DR site.
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