Snapshot deletion performance impact

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Snapshot deletion performance impact

basilberntsen
Hi folks, I need to delete a bunch of snapshots that were orphaned by CDOT when someone changed the schedule. It's a lot of data- 500gb for a 1tb LUN. How does ontap prioritize releasing these blocks after the delete? What's the best way in 8.2.3 to measure the impact, if any? 
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Re: Snapshot deletion performance impact

John Stoffel-5

Basil> Hi folks, I need to delete a bunch of snapshots that were
Basil> orphaned by CDOT when someone changed the schedule. It's a lot
Basil> of data- 500gb for a 1tb LUN. How does ontap prioritize
Basil> releasing these blocks after the delete? What's the best way in
Basil> 8.2.3 to measure the impact, if any? 

I wouldn't worry about it.  The disk blocking freeing happens in the
background and higher priority stuff will take precedence in my
experience.  Yes, it will put a load on the system, but if the system
is beefy enough, or you have enough spindles and the disks aren't
already too busy, you should be fine.

Maybe the output of:

   statistics show-periodic -object disk:raid_group  -instance /.....

will give you some idea of how busy you are?

Or you could do:

  statistics start -object aggregate

wait a bit...

  statistics show -object aggregate

and turn off stats with:

  statistics stop -object aggregate

But honestly I'd just google 'ontap cdot vmstat' and look there for
tricks to run.  *grin*

John

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