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 Post subject: Snapshoting many volumes at once...
PostPosted: Thu Aug 08, 2019 10:33 am 

Joined: Wed Jan 16, 2019 4:26 pm
Posts: 28
Location: Florida
We were told snapshot schedules should be staggered. I've started snapshotting a vvset with 96 volumes and seeing their I/O stunned for less than two seconds which causes no issues for us.

What are the best practices here?


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 Post subject: Re: Snapshoting many volumes at once...
PostPosted: Tue Aug 13, 2019 11:32 pm 
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Joined: Tue Aug 18, 2009 10:35 pm
Posts: 1223
Location: Dallas, Texas
It depends on factors like which model of controller, how many nodes, how busy the array is, change rate, what other features are in use. You are aware of the stun time, and ok with 2 seconds. It sounds like you are managing and administering *your* environment within you tolerances.

Be aware that the larger the consistency group, the more work the array has to do. Dogpiling other feature on like dedupe, remotecopy, filepersona, compactcpg, many old snapshots in the tree, plus workload spikes can push you over your scsi timeout if you are not careful. You can counter that by increasing your scsi timeouts (to a point) or scaling back/staggering some of the expensive features and workload.

If you have a business requirement for a consistency group that large, then your hands are tied, and proceed with caution, avoid dogpiling. If you don't have a requirement for a consistency group that large, split it up and stagger it for future proofing.

I recommend a call to support for specific guidance that considers your specific array hardware, options enabled, code level and patches.

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Richard Siemers
The views and opinions expressed are my own and do not necessarily reflect those of my employer.


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 Post subject: Re: Snapshoting many volumes at once...
PostPosted: Wed Aug 21, 2019 5:46 pm 

Joined: Wed Jan 16, 2019 4:26 pm
Posts: 28
Location: Florida
Excellent response! Thanks for the detailed answer. These are simple VMFS datastores and a handful of LUNs passed-through as RDMs. There's no requirement for snapshot consistency here. I just want to use a vvset for snapshot scheduling because I'm lazy. :-)

Add a new datastore; add to the vvset. Decom a datastore; remove from the vvset. Makes things easy while we're transitioning datastores and arrays.


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