ONTAP Discussions

Snapshot changes

ACHOU_SIMG
2,894 Views

ONTAP 8.3GA

 

Hi,

 

If I take a snapshot of a volume and I see that snapshot's size changes every minute, is it safe to conclude there has been data changes in that volume since the snapshot was taken? I thought so but just want to make sure I don't miss anything.

 

Thanks,

 

1 ACCEPTED SOLUTION

aborzenkov
2,848 Views
Snapshot "size" never decreases. It is amount of data changed since snapshot had been taken. Deduplication/compression change data as well (not user visible data, but what is actually stored on volumes), so they cause snapshot growth.

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3 REPLIES 3

AlexDawson
2,871 Views

Yes - safe, but not 100% - it may be changing due to background ONTAP processes, such as deduplication, compression, but most likely from clients reading or writing data (read time updates will change metadata, so snapshot size - so it doesn't necessarily mean write, but often does)

ACHOU_SIMG
2,860 Views

Thanks, Alex.

 

In my case, I have observed snapshot sizes only increase so it does not look like to be the result of deduplication/compression. I have concerns about this because in my scenario all the servers mounting to this set of volumes have been powered off but I still see these volumes' snapshots grow at a steady rate after snapshots are taken. I suspect there are other servers mounting to the volumes as well.

 

Thank you.

aborzenkov
2,849 Views
Snapshot "size" never decreases. It is amount of data changed since snapshot had been taken. Deduplication/compression change data as well (not user visible data, but what is actually stored on volumes), so they cause snapshot growth.
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