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Restoring VM differentials - is GRT/noGRT a problem?

Created: 11 Sept. 2013 • Aktualisiert: 19 Sept. 2013 | 4 Kommentare
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Hi folks,

(Environment:  I have BE 2010 R3 SP2+HotFixes  with VMware ESXi 4.1)

I'm running a restore of a full VM to a Testlab cluster in our VM environement, and it's not going well.

I've read up on the How To parts, and am selecting just the Differential of the date I want.  Differentials & the associated Full are part of the same policy, I'm using NBD transport, and doing a VM redirect into the Testlab.  The redirect is fine, and the job completes succesfully -- but when I power on the VM, I get a blank screen and a single  _  for a cursor, which doesn't curse at all anyway..  I've run the job from both tape media, and the B2D media.

Notably, the Job only restores 2.3 Gb of a ~30 Gb VM.  And both Job Logs indicate that they only used media from the Tuesday (target) and Monday differential backups... not the previous Friday Full backup set.

The Diff and Full backups are directed to different B2D folders, and duplicate to different tapes - naturally enough.  But the reason I have them going to different B2D folders is because the Best Practices for B2D folders says to separate GRT and non-GRT backups in this way.

I looked at the Full backup, and indeed it is a GRT, but the Differentials are not.  This is because VM backup Best Practices say that you cannot use GRT for Differential backups of a VM.  Indeed, when I took over from my predecessor, several VM differential jobs with GRT selected would irregularly encounter a 9598 error.

So the Full backup is directed to an IMGxxxxx file, and the Differential backups go to B2Dxxxxx files.

Is this the problem?  If I mix GRT-Full and non-GRT-Diff backups of VMs... the differential restore breaks?

Does this sound correct?   I would like to have the option to pull individual files from my VM backups (GRT)... but I would much rather be able to restore differentials, otherwise all those differential backups are a waste of magnetic space!

Please advise.

Thank you.



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But the reason I have them going to different B2D folders is because the Best Practices for B2D folders says to separate GRT and non-GRT backups in this way.

I am surprised because for BE 2012, you can only have 1 B2D folder per volume. So if you have only one volume in your media server, this will be a problem.  Can you provide the link this this best practice?  

If I mix GRT-Full and non-GRT-Diff backups of VMs... the differential restore breaks?

No.  It will not.

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I don't think you can mix GRT and non GRT with VMware  full and differential in the way you are doing as the recovery (and differential re-assmbly) process of the two backup types being different is likely to cause a problem. One thing to note is that in BE 2012  you cannot disable GRT on the diff and leave it on the full - we almost certainly limited it like that to stop customers from making a choice that won't work.

Have you tried still using two B2D folders but with GRT enabled on both full and diff and then do a restrore test form that? (or set both to non-GRt and then test with that)

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pkh: Sure, however I'm talking about BE 2010, not 2012. ---> "Create a separate backup-to-disk folder specifically for all GRT enabled backup jobs" (TECH164267)

Colin: Ok, good to know.  I hadn't run across any documentation that stated or even really inferred that mixing GRT on/off for full/diff backups on VMs would be a problem.  I haven't tested what you suggest yet, as I just discovered the problem.  I will be turning GRT off for all VM backups this weekend, however, and thoroughly testing it next week.  And yes, for the time being I will keep the different B2D folders.  Happy to post back here next week when I know the results.  I would be surprised if full/diff's going to different destinations causes a problem, because it would be rather common to direct a full to one tape, and a differential to another tape (prior to using disk backups), but I'll check it out to be sure.

I have some trepidation to using GRT on differential VM backups, because I have had problems with those in the past.  So I'll just turn the GRT off completely on those VM jobs.




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Just to touch back on the incidental question:  I turned off GRT on the full backups of our virtual machines (where there was no GRT on the differential backups), and I've tested recovery from both Disk and Tape media... there is zero problem recovering a full, operational VM from either media when the full backups are pointed at one B2D directory, and the differentials of that same VM (same job policy) are pointed at a different B2D directory.

Conversely, I have one GRT backup on one virtual machine using AVVI;  GRT is set on both full and diff.  So far, no problems, and I can recover files w/o issue.  (Again, the destination B2D and tape media are different).  I will continue testing this further next week, but so far so good.