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Is it possible to look/open a VMWare delta file

Posted on 2012-03-16
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Last Modified: 2012-03-17
We were having loads of issues with our SAN dropping connections and doing some really weird stuff so the decision was made to vmotion all disks to local storage, wipe the SAN and start again.

So thats what we did. Except now there are a few files/folders which are missing, and apparently not where they should be.

The only thing we can think of is that the fileserver had an unidentified 8GB delta (vmname-000001-delta.vmdk) left over in the SAN even after we'd migrated off.

We copied this off before wiping the SAN.

Is it possible our data is in this file? If so, how can we open it?

No backups either, they were failing all over the place becuase of the SAN issues.
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Question by:hongedit
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Andrew Hancock (VMware vExpert / EE MVE) earned 500 total points
ID: 37730747
This is the Snapshot Delta file, your data will be in this file, but you need to have the Parent Disk to the Child Snapshot file, to merge before you can check the data.

If you only have the Delta disk - No.


A snapshot is NOT a backup of a VM; that is a gross misconception.  

A snap shot is a way to preserve a point in time when the VM was running OK before making changes. A snapshot is NOT a way to get a static copy of a VM before making changes.  When you take a snapshot of a VM what happens is that a delta file gets created and the original VMDK file gets converted to a Read-Only file.  There is an active link between the original VMDK file and the new delta file.  Anything that gets written to the VM actually gets written to the delta file.   The correct way to use a snapshot is when you want to make some change to a VM like adding a new app or a patch; something that might damage the guest OS. After you apply the patch or make the change and it’s stable, you should really go into snapshot manager and delete the snapshot which will commit the changes to the original VM, delete the snap, and make the VMDK file RW. The official stance is that you really shouldn’t have more than one snap at a time and that you should not leave them out there for long periods of time. Adding more snaps and leaving them there a long time degrades the performance of the VM.  If the patch or whatever goes badly or for some reason you need to get back to the original unmodified VM, that’s possible as well.  

I highly recommend reading these 2 articles on VMware Virtual Machine Snapshots:

Understanding Snapshots - http://kb.vmware.com/kb/1015180
Snaphot Best Practices - http://kb.vmware.com/kb/1025279

Also check out the following Snapshot Articles by Eric Siebert

Pt.1- http://is.gd/Lajg4p
Pt.2- http://is.gd/NdKQWC
Pt.3- http://is.gd/tp2vEK
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by:hongedit
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I know about snapshots, and we weren't knowing running any - I learnt the hard way before.

The only reason a snapshot would be there is I think, due to a failed veeam backup.

I've been reading it is possible to recover data from just a delta file but it requires indepth knowledge about the old base disk which is now gone, and even then its a specialist job - I dont think the data is worth that much, as we have restored a semi-recent verswion of it.
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by:Andrew Hancock (VMware vExpert / EE MVE)
Andrew Hancock (VMware vExpert / EE MVE) earned 500 total points
ID: 37733167
If you do not have the parent disk, you would need to use a company like Kroll Ontrack.
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