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Netapp Snapshot Reserve Edumacation 3Q in One

Let's say I have a 100GB Volume with 20% dedicated to snapshot reserve.  

-Does that mean that my snapshots will never take up more that 20GB of space?
-At what point do old snapshots get deleted as they approach the 20GB snap reserve limit?  

Suppose you had a LUN in the 100GB volume and it tried to grow to 90GB while say there .  were 15GB of snaps in snap reserve.  What would happen?  

Thank you.
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amigan_99
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amigan_99
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1 Solution
 
robocatCommented:
Snapshot reserve is not an upper limit, snapshots can grow beyond the reserve and occupy volume space. The snapshot reserve is a guarantee that snapshots will not fail even if the volume is otherwise full. Snapshot reserve is often set to zero, because it has a limited usefulness.

There is a volume option to autodelete snapshots, but this is not triggered by the snapshot reserve being full, but by the entire volume being full.

Be aware that both fractional reserve (for LUNs) and snapshot reserve take away usable volume space. Don't use both in the same volume.
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Paul SolovyovskyCommented:
Snapshot reserve is not a guarantee, a snapshot will grow out of the space allocated for snapshot reserve. Snapshot reserve is just used for accounting.

Let's say you have a CIFS volume that's 100GB with snapshot reserve of 20%.  The CIFS volume will show up as 80GB volume and 20GB will be used for snapshot reserve.  But let's say that your snapshots grow to 30GB, your volume will show up as still 80GB but your usable space will decrease by 10%.  Best way to mitigate this is to use the auto delete feature (as mentioned above) where the volume will delete the oldest snapshot

Typicall where you have block you do not set snapshot reserve.  You should also use space reclaimation on your log volumes/backup volumes as LUNs will get fragmented and can run out of space even though OS may show plenty of storage still available.
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amigan_99Author Commented:
Thank you.  Looking like I have some changes to make!  The earlier admin had setup a 20% snap reserve pretty much everywhere including some very large volumes.
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Paul SolovyovskyCommented:
You will need to baseline what your usage is.  You can either thick or thin provision LUNs, change snap reserve, etc..  What model SAN are you running and what are you using it for?
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amigan_99Author Commented:
We have a FAS 3140 and we connect to it via 10Gig ISCSI.  On the other end is two chassis Cisco UCS multi-blade and Nexus.  Most of the VMs are Windows 2008 - usual business stuff like Exchange, DCs, Sharepoint, Lync, Office, MS SQL yada yada.  We have some CIFS served up by the filer but small in comparison with everything else.
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Paul SolovyovskyCommented:
We put one of these in a few weeks ago and there was an issue with the 3140 and the Nexus where we had to to use an RC version of Ontap to resolve.

Check best practice for SME and SMSQ, make sure you use the space reclamation on the LUNs otherwise you may get into trouble.  Install Config Advisor and check the configuration every once in a while, it will tell you what upgrades you may need, somewhat like upgrade advisor online.
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amigan_99Author Commented:
I've never tried Config Advisor.  Sounds interesting.  Is that within Ops Manager or Filer View?  I haven't setup System Manager yet.  Can that run on the same box as NetApp Operations Manager?
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Paul SolovyovskyCommented:
It's a standalone tool on the support site (now.netapp.com)n it as a standalone utility
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amigan_99Author Commented:
Cool - I have an account there.  I will look it up for sure.
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