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BCT-Tech
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Skip VSS or enable Crash Consistent?

Post by BCT-Tech » Feb 08, 2018 10:35 pm

Case # 02531465

We have a couple of older VMs (2003 R2 and SBS 2008) that always fail VSS Application Aware Processing.

Currently, we have them set to "try application processing, but ignore failures" - and the VMs complete with a warning that Guest processing was skipped.

We don't want to spend too much time troubleshooting the VSS issues, because the Servers will be decommissioned in the near future.

Is it better to set the VMs in that job to "try application processing, but ignore failures" or disable AAP and enable Hyper-V guest quiescence and take crash consistent backup?

Mike Resseler
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Re: Skip VSS or enable Crash Consistent?

Post by Mike Resseler » Feb 09, 2018 6:42 am

Hey BCT-Tech,

That will depend. What workloads are those VMs running. The SBS 2008 I'm a bit scared off because it most probably runs exchange and AD and a crash consistent backup might be not the best idea when you need to restore.

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Re: Skip VSS or enable Crash Consistent?

Post by nmdange » Feb 09, 2018 3:37 pm

If you enable Hyper-V Native Guest Quiescence, then the Hyper-V integration services will initiate a VSS snapshot in the guest as long as "Backup (Volume Snapshot)" is enabled in the integration services, so it will still be application consistent. If the issue is with VSS in the guest, then it will most likely fail using native quiescence as well, but it's worth trying to see if there is a difference.

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Re: Skip VSS or enable Crash Consistent?

Post by BCT-Tech » Feb 09, 2018 4:18 pm

nmdange wrote:If you enable Hyper-V Native Guest Quiescence, then the Hyper-V integration services will initiate a VSS snapshot in the guest as long as "Backup (Volume Snapshot)" is enabled in the integration services, so it will still be application consistent. If the issue is with VSS in the guest, then it will most likely fail using native quiescence as well, but it's worth trying to see if there is a difference.
Are you talking about enabling Hyper-V Native Guest Quiescence, but not crash consistent backup?

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Re: Skip VSS or enable Crash Consistent?

Post by BCT-Tech » Feb 09, 2018 4:27 pm

Mike Resseler wrote:That will depend. What workloads are those VMs running. The SBS 2008 I'm a bit scared off because it most probably runs exchange and AD and a crash consistent backup might be not the best idea when you need to restore.
Exchange has been "disabled" on that Server, and it is their only Domain Controller for now.

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Re: Skip VSS or enable Crash Consistent?

Post by nmdange » Feb 09, 2018 5:31 pm

BCT-Tech wrote: Are you talking about enabling Hyper-V Native Guest Quiescence, but not crash consistent backup?
The setting "Take crash consistent backup instead of suspending VMs" in Veeam is really only applicable to Windows Server 2012 R1 and earlier, which used to suspend VMs that could not do online backups. As long as you have "Backup (Volume Snapshot)" enabled in the properties of the VM in Hyper-V, it will do an in-guess VSS snapshot and if that fails, the backup will fail with a VSS error, it does not fall back to crash-consistent. To do that you have to disable that integration services setting on the VM in Hyper-V.

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Re: Skip VSS or enable Crash Consistent?

Post by BCT-Tech » Feb 09, 2018 9:57 pm

nmdange wrote:The setting "Take crash consistent backup instead of suspending VMs" in Veeam is really only applicable to Windows Server 2012 R1 and earlier, which used to suspend VMs that could not do online backups. As long as you have "Backup (Volume Snapshot)" enabled in the properties of the VM in Hyper-V, it will do an in-guess VSS snapshot and if that fails, the backup will fail with a VSS error, it does not fall back to crash-consistent. To do that you have to disable that integration services setting on the VM in Hyper-V.
Won't native quiescence pause the VM while it is being backed up?

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Re: Skip VSS or enable Crash Consistent?

Post by nmdange » Feb 11, 2018 3:43 pm

No that behavior is only applicable to Windows Server 2012 R1 and earlier. 2012 R2 and later do not pause VMs during backup. https://blogs.msdn.microsoft.com/virtua ... s-anymore/

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Re: Skip VSS or enable Crash Consistent?

Post by BCT-Tech » Feb 12, 2018 4:30 pm

nmdange wrote:No that behavior is only applicable to Windows Server 2012 R1 and earlier. 2012 R2 and later do not pause VMs during backup. https://blogs.msdn.microsoft.com/virtua ... s-anymore/
Just to verify - you are talking about the Host correct? As long as the Hyper-V Host is 2012 R2 or newer the VMs will not pause?

Or are you talking about if a VM is 2012 R1 or older?

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Re: Skip VSS or enable Crash Consistent?

Post by nmdange » Feb 12, 2018 5:31 pm

Yes sorry, as long as the Hyper-V host is 2012 R2 or newer. Guest OS does not matter.

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Re: Skip VSS or enable Crash Consistent?

Post by BCT-Tech » Feb 12, 2018 5:35 pm

OK, I will change the job to disable AAP and enable Hyper-V Native Guest Quiescence, but not crash consistent backup.

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Re: Skip VSS or enable Crash Consistent?

Post by BCT-Tech » Feb 13, 2018 5:00 pm

All VMs backed up successfully last night with these settings.

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Re: Skip VSS or enable Crash Consistent?

Post by Nail.Mukhametshin » Feb 14, 2018 7:58 am

BCT-Tech, check this feature request: microsoft-hyper-v-f25/feature-request-i ... 38197.html. May be this that you need. If so, please post there "+1" message. I think this can help to provide this feature request faster ;)
Nail Mukhametshin | System Engineer | R&D Services Infrastructure Development | Kaspersky Lab

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