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MSA2012fc snapshot question - content not updating

 
Samuel Record
Occasional Visitor

MSA2012fc snapshot question - content not updating

I am confused by the following behavior that I am seeing with snapshots on a MSA2012fc. Can someone explain why this is the case?

1) A snapshot of a master volume is mounted on a host. The host is able to access the snapshot OK. The contents of the snapshot appear to be an accurate reflection of the master volume at some previous point in time.

2) Modifications are made to the master volume. In this case, two files are deleted from the root directory, and a third file is added.

3) The snapshot is unmounted from the host.

4) The filesystem on the host owning the master volume is synced (using the sysinternals/MS sync.exe utility) to ensure that the changes made in step 2 have been flushed to disk.

5) The snapshot is reset (according to the documentation, "You can reset a snapshot to replace its content with the current data state of the associated master volume").

6) The snapshot is mounted on the host once again. However, the changes that were made in step 2 are not visible. The files that were deleted in step 2 are still present in the snapshot, and the file that was added in step 2 is not present in the snapshot.

If I am misunderstanding the documentation, what are the necessary steps to reliably refresh the content of the snapshot?

Both hosts in this scenario are running Win2K3 R2 SP2.

Storage Controller Code Versions
RAID Controller A RAID Controller B
Code Version J200P24 J200P24
Memory Controller F300R22 F300R22
Loader Version 15.010 15.010

Management Controller Code Versions
RAID Controller A RAID Controller B
Code Version W420R45 W420R45
Loader Version 12.013 12.013

Enclosure Controller Code Versions
RAID Controller A RAID Controller B
Code Version 3019 3019


Thanks,
Sam Record
5 REPLIES 5
Highlighted
raadek
Honored Contributor

Re: MSA2012fc snapshot question - content not updating

Sam,

I must admit I am not familiar with MSA2000 snapshotting capabilities in great detail, but...

Typically snapshots are read-only, point-in-time, logical copies of the master volume / LUN. So if there is any new change to the master volume you want to protect, the simplest (& usual) way to do this, is to create a new shapshot.

Depending on your preferences / circumstances (disk space, performance, housekeeping) you may either retain or destroy 'old' snapshot(s).

Regards.
Don't panic! [THGTTG]
Samuel Record
Occasional Visitor

Re: MSA2012fc snapshot question - content not updating

Thanks for the response. If it's necessary to create a new snapshot to gain access to new data, so be it - however, my understanding from HP is that unmounting, resetting and remounting the snapshot should be sufficient. I have a case open with them now and will post any findings here.

Sam
Uwe Zessin
Honored Contributor

Re: MSA2012fc snapshot question - content not updating

As a test, can you reboot the server before it mounts the new snapshot? Windows is sometimes too eager in keeping cached data.
.
Peter A Day
Occasional Visitor

Re: MSA2012fc snapshot question - content not updating

Hi Sam,

Iâ m wondering if you ever found a resolution to this.

I am facing a similar scenario with Snapshots on a MSA2324fc.

I can present a Snapshot to my backup server and it accurately reflects the data at the point the snapshot was taken.

My issue is with how to automate my backups. I can schedule a snapshot reset, however, I am struggling with how to get my Win2k3 R2 server to see the refreshed data.

Can you tell me if you have come up with a good solution to this. If so, would you mind letting me know the process you are using for your Un-mount/Remount/Refresh process

Any help would be greatly appreciated.

Any thoughts from anyone else?

Cheers

Peter
Samuel Record
Occasional Visitor

Re: MSA2012fc snapshot question - content not updating

Hi Peter,

>>>>> My issue is with how to automate my backups. I can schedule a snapshot reset, however, I am struggling with how to get my Win2k3 R2 server to see the refreshed data.

My problem turned out to be that I was using the mountvol command with the /D switch to dismount the SAN volume from the server. I found that I needed to use the /P switch instead. Apparently the mount point needs to be recreated in order for W2K3 to see the updated data. Fortunately the mount point ID appears to remain constant between iterations so the process is simple to script.

>>>>> Can you tell me if you have come up with a good solution to this. If so, would you mind letting me know the process you are using for your Un-mount/Remount/Refresh process

The process is basically as follows:

1) determine mount point ID of snapshot volume
2) use mountvol /P to dismount volume
3) reset snapshot
4) use mountvol to remount volume

In my case, the mount point ID is \\?\Volume{2c1c9291-bbc8-11dd-bd3b-002264c1de48}\

Hope this helps (also, thanks for jogging my memory - I had forgotten that I promised to update the thread!).