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QUESTION - concerns around "dfpm_base" snapshot

Hello everyone

I have some Qs from a client which is a little tough for me to answer.  Let me paste them here "word for word" and I will comment after on what i believe the answer is.  THere seems to be a lot of concerns around the size and growth of the DFPM base snapshots at this installation.  I do not know yet if they are removing dfpm base lines yet, I will know more in a few days.

I have a situation, in my volume I need to remove 500GB sized directory. I know that I don’t need it as it has been archive to tape(requested by user). So my question is, once I delete 500GB from my volume, it will contribute to “dfpm_base” snapshot. How can I prevent this from filling “dfpm_base” , I am confirmed that it is not required. What will happen if I removed “dfpm_base”?

Not sure how they confirmed it but the DFPM_BASE is critical to the operation of snapvault/mirror right?

This question is quite similar with question above. If I removed “dfpm_base” , I can still restore previous backup from snapvault?( I have tested working, just want to confirm).

Your destination snapshots are still there but without the "base" you are not getting anymore updates


What will happen if I remove “dfpm_base” snapshot accidently?

future updates will not happen.

How to protect the dfpm snapshot (on the primary) from being deleted by snap autodelete

The DFPMbase should be a "busy" snapshot; i have seen this before at other sites and this was over a year ago, not sure if the technology has changed where autodelete ignores the base snapshots

thanks for your time.

Re: QUESTION - concerns around "dfpm_base" snapshot

Your answers all look correct to me.

Your client is running into a fundamental behavior of snapshot copies: if you use snapshots, you don't reclaim space when you delete files. You must also delete any snapshot copies created prior to deleting the files.

In order to free up the space pinned down by the dfpm_base snapshot, run a scheduled or ad-hoc backup. That creates a new dfpm_base snapshot and deletes the old one, which will free up the blocks. However, if there are any other snapshots pinning down the space (i.e daily, weekly or monthly backups on the primary volume), your client will still not see space freed up.

-- Pete

Re: QUESTION - concerns around "dfpm_base" snapshot

I will have to ask them about their schedules to see if they have nightlies or other scheduled snaps in line because to reclaim space, they will need to have those expire.

very interesting about the dfpm_base ... I can force a scheduled backup to take place?  ( the ad-hoc is the "backup now" ) selecton.  This can be a good method to help a couple of backups that get stalled on space but hopefully it will not become a common practice; if it does the larger problem is space utilization.

Re: QUESTION - concerns around "dfpm_base" snapshot

Had the meeting with Altera; good discussion; will be following up with action items