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How do I Overwrite SFW Snap Shots?

I am testing a new backup soultion for my group and have been playing with Snap/Snap Shots. Everything works just how I need it to until it is time to overwrite an old Snap Shot. The only way I have found that I can reuse the disk is to Snap Clear, Delete the Volume then Prepare again before I am ready to take the new Snap Shot. I have to be doing somthing wrong. How can I drop a new Snap Shot overwriting to old without have to go thought all this or without using the Snap Back as I dont want to overwrite my good data?

1 Solution

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Accepted Solution!

You use snapback - this will

You use snapback - this will not overwrite your good data - you woukd use resyncfromreplica option if you wanted to overwrite original data with snapshot data.

Just to clarify:

You start with volume A which has normal plex A and snapshot plex B (i.e volume A contains 2 copies of data - plex A and plex B)

You create a snapshot B so that volume A, now JUST has plex A and you have a new snapshot B volume with plex B.

If you use snapback, then contents of plex B gets overwriten with contents of plex A in volume A and snapshot B must be unmounted to do this.

If you use snapback with resyncfromreplica option then plex A gets overwritten with contents of plex B - i.e volume A get overwritten with data in snapshot B and to do this you must unmount volume A first.

If you are ever unsure which way copy is going to go, then mount the filesystem you want and then if you use the wrong option, it will fail as mounted filesystem will be "open" so it cannot be written to from snapshot command.

Mike

 

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3 Replies
Accepted Solution!

You use snapback - this will

You use snapback - this will not overwrite your good data - you woukd use resyncfromreplica option if you wanted to overwrite original data with snapshot data.

Just to clarify:

You start with volume A which has normal plex A and snapshot plex B (i.e volume A contains 2 copies of data - plex A and plex B)

You create a snapshot B so that volume A, now JUST has plex A and you have a new snapshot B volume with plex B.

If you use snapback, then contents of plex B gets overwriten with contents of plex A in volume A and snapshot B must be unmounted to do this.

If you use snapback with resyncfromreplica option then plex A gets overwritten with contents of plex B - i.e volume A get overwritten with data in snapshot B and to do this you must unmount volume A first.

If you are ever unsure which way copy is going to go, then mount the filesystem you want and then if you use the wrong option, it will fail as mounted filesystem will be "open" so it cannot be written to from snapshot command.

Mike

 

View solution in original post

So let me see if I understand

So let me see if I understand when I Snap Back I get a popup that ask    1:Resyncronize using the original volume   2: Resyncronize using the Snap Shot.  So if I select 1 then the data will stay the same but the snapshot is released. If I select 2 then I overwrite my data.

You can do snapshots with

You can do snapshots with vxassist, vxsnapshot or GUI - if you are using vxassist, there is no prompt, but not sure about GUI as I never use it.  Using vxassist you can do:

  1. vxassist -g diskgroup -o resyncfromreplica snapback snapvolume (copy from snapshot to overwrite original volume)
  2. vxassist -g diskgroup -o resyncfromoriginal snapback snapvolume (copy from original volume to overwrite snapshot)
  3. vxassist -g diskgroup -snapback snapvolume (this copies from original volume to overwrite snapshot as this is default)

So I would do option 3 (but of course, you can use option 2 also)

Mike