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Question about remote copy
https://www.3parug.com/viewtopic.php?f=18&t=2734
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Author:  jbguy [ Thu Nov 30, 2017 11:34 am ]
Post subject:  Question about remote copy

Good afternoon all. First post here.

I recently came into a roll that uses 3PAR a few months back and am still learning the ropes.

We recently enabled Remote Copy and its running well but I was examining one of our 3PARs and noticed that it now has a lot more space used. I took a look at the CPG and it shows that there are 20tb of snapshots which is weird since I have never done snapshots.

The VVs that have the snapshots appear to be the Volumes that are being remote copied. Am I correct to assume these are from that operation?

Author:  MammaGutt [ Thu Nov 30, 2017 1:11 pm ]
Post subject:  Re: Question about remote copy

Remote copy uses snapshots directly(async/periodic) and indirectly (sync).

Async will write all changes to a snapshot which is transferred at set intervals and sync will use a snapshot to keep track of changes when the rc croup is stopped.

You can do "showvv - s" in CLI/SSH too see the space used by each volume. If snap space is reserved and no snapshots are seen (async snapahots are visable) you could do "freespace <vvname> to release the space back to the CPG.

Author:  jbguy [ Thu Nov 30, 2017 2:12 pm ]
Post subject:  Re: Question about remote copy

MammaGutt wrote:
Remote copy uses snapshots directly(async/periodic) and indirectly (sync).

Async will write all changes to a snapshot which is transferred at set intervals and sync will use a snapshot to keep track of changes when the rc croup is stopped.

You can do "showvv - s" in CLI/SSH too see the space used by each volume. If snap space is reserved and no snapshots are seen (async snapahots are visable) you could do "freespace <vvname> to release the space back to the CPG.


Thanks for the information. We use periodic for our replication method.

I ran the command and there is a reserved value. We don't use snapshots so i'm assuming this is for the remote copy process. Is it safe to use the free space command while data is still replicating?

Author:  MammaGutt [ Thu Nov 30, 2017 4:17 pm ]
Post subject:  Re: Question about remote copy

With periodic you always have at least one active snapshot so you can't use freespace. It will give an error stating it has active snapshot if you try.

Author:  jbguy [ Fri Dec 01, 2017 9:58 am ]
Post subject:  Re: Question about remote copy

MammaGutt wrote:
With periodic you always have at least one active snapshot so you can't use freespace. It will give an error stating it has active snapshot if you try.


Thanks for the information.

Will the snapshot always be so large or does it go down once the initial seed is complete?

Author:  jbguy [ Tue Dec 05, 2017 9:48 am ]
Post subject:  Re: Question about remote copy

Just bumping this one to see if there is any other information people might have on it.

Right now I have over 30tb of snapshots for the periodic remote copy and it doesnt seem to go down. We only have 8.3tb free overall and Im wondering why my other 3PAR didnt eat up that much snapshot space.

Thanks.

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