Discussions specific to the Microsoft Hyper-V hypervisor
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MarcelB
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Backup of Hyper-V servers

Post by MarcelB »

This might be the first technical question on the upcoming feature of B&R for Hyper-V backups.

When System Center Data Protection Manager 2010 (DPM) is protecting Hyper-V guests using the Microsoft Software Shadow Copy provider (the VSS provider), DPM will be using software snapshots when backing up guests located on Cluster Shared Volume (CSV) disks. While the backup is in progress, the CSV will remain in re-directed access mode for the duration of the guest backup. This means all disk I/O for Guests located on that CSV will be in redirected mode and be going over the network instead of direct access to the CSV and performance may be affected.
Microsoft recommends to use of hardware snapshots. http://support.microsoft.com/kb/2473194

Will this be the same for backups made by Veeam B&R?

regards,
Marcel

Gostev
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Re: Backup of Hyper-V servers

Post by Gostev »

Hi Marcel, you are correct that software VSS provider requires redirected I/O for the duration of backup, no matter of backup solution used. However, there is really no point of using software VSS provider when backing up VMs from Cluster Shared Volumes. CSV requires using shared storage, but all major shared storage vendors implement hardware VSS providers. In fact, even the now free Microsoft iSCSI Target ships with hardware VSS provider. So, I do not really see why would anyone want to use software VSS provider with CSV?

KOOLER
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Re: Backup of Hyper-V servers

Post by KOOLER »

Microsoft hardware VSS is a fake one. It's not enough to do CSV snapshot in the proper way. Read this:

http://social.technet.microsoft.com/For ... 7e73c55ad/

and this:

http://blogs.technet.com/b/dpm/archive/ ... table.aspx

P.S. Datacore and Falconstor also have hardware VSS providers. Also fake ones :)

Gostev
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Re: Backup of Hyper-V servers

Post by Gostev »

Hardware VSS provider that comes with Microsoft Storage Server is fine, although it does require some know-hows when working with. This is actually one of the platforms we test our v6 with, and we are not seeing any issues leveraging hardware VSS with the current v6 code.

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Re: Backup of Hyper-V servers

Post by KOOLER »

The whole idea of having VSS provider is keeping everything isolated inside VSS provider + SAN link. Modifying backup app (calling extra VSS things to prepare a snapshot) to explore functionality expected to work out of box mean "DOES NOT WORK". What you do we call a "workaround" and not a solution. Good you've managed to have everthing running but you did something I beleive is MS job...

tux-
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Microsoft Hardware VSS + Offhost Processing

Post by tux- »

[merged]

Hi,

According to this thread: Backup of Hyper-V servers
Microsoft iSCSI target VSS hardware provider (connecting to iSCSI target on Windows Storage Server 2008R2) is supported as an hardware VSS provider for Offhost backup processing.

WIth Microsoft DPM; it isn't (even though, it's their own product). Microsoft Hardware VSS for iSCSI target does not support auto-recovery snapshots, and therefore is not suitable for use with DPM 2010 (it bails out with a transcient VSS error).
In fact, it does support transportable snapshots so therefore chances are it might work with Veeam.

Could anyone confirm this is in fact working and/or supported? If so, Veaam will have a new and happy user :)

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Re: Backup of Hyper-V servers

Post by Gostev »

I have already confirmed in my previous post :D

tux-
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Re: Backup of Hyper-V servers

Post by tux- »

Thanks for the confirmation. Today, I grabbed a bunch of hardware and tried it myself. Pretty impressive, as it seems to work (even though, auto recovery snapshots are not supported according to Microsoft). The only thing is, the snapshot is not deleted after the job completes. Is there a way to accomplish this?

foggy
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Re: Backup of Hyper-V servers

Post by foggy »

I would first check vssadmin list writers on the proxy server for errors (whether writers are stable, etc.).

tux-
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Re: Backup of Hyper-V servers

Post by tux- »

The Microsoft Hardware VSS provider seems not to work with Veeam offhost backup processing. It fails in the snapshot auto-recovery phase, with errors 10110 and 10111 on the Hyper-V host. This is exactly the same as with Microsoft DPM. As long as the auto-recovery VSS technology is used; the Microsoft Hardware VSS provider will not work in the Off-host Hyper-V backup scenario. With on-host processing, it seems to work however snapshots are not being cleaned up after the backup finishes, and in fact it is not sure whether the backups are valid in VSS terms.

The only option is, to use the Software VSS provider; which is basically not an option in terms of performance.

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Re: Backup of Hyper-V servers

Post by tux- »

@ Anton Gostev: Are you sure this specific scenario has been succesfully tested? Hyper-V backup on Cluster Shared Volume, using Microsoft Hardware VSS provider (for MS iSCSI target) and offhost processing?

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Re: Backup of Hyper-V servers

Post by tux- »

Okay, after some fiddling; I've got the setup working. However, two things are still bothering me:

[*] Snapshots are still not being deleted after the backup completes.

I would like the snapshots to be auto-deleted to avoid performance impact and clutter on the storage boxes.

[*] Hyper-V VSS writer is still logging 10110 and 10111 (could not find virtual hard disk, and no snapshot to revert)

I see snapshots being exposed read-only to the offhost proxy, and the backup continues as normal. However, the hyper-V VSS writer is logging those errors what seems to me is the auto-recovery phase of the snapshot failing in which the external snapshot is reverted to the state of the internal snapshot.
This seems plausible, as auto recovery snapshots are not supported in Microsoft iSCSI hardware VSS (in fact the reason why DPM doesn't support it). Could anyone at Veeam confirm this, or am I missing something?

Thanks

foggy
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Re: Backup of Hyper-V servers

Post by foggy »

tux- wrote:[*] Snapshots are still not being deleted after the backup completes.
I would like the snapshots to be auto-deleted to avoid performance impact and clutter on the storage boxes.
This is just how the Microsoft iSCSI Software Target works. It stores snapshots while it has space available and then starts to delete the oldest ones.
tux- wrote:[*] Hyper-V VSS writer is still logging 10110 and 10111 (could not find virtual hard disk, and no snapshot to revert)

I see snapshots being exposed read-only to the offhost proxy, and the backup continues as normal. However, the hyper-V VSS writer is logging those errors what seems to me is the auto-recovery phase of the snapshot failing in which the external snapshot is reverted to the state of the internal snapshot.
This seems plausible, as auto recovery snapshots are not supported in Microsoft iSCSI hardware VSS (in fact the reason why DPM doesn't support it). Could anyone at Veeam confirm this, or am I missing something?
Yes, Hyper-V backup is not supported and this is covered in iSCSI Software Target release notes:
Hyper-V host backup is not supported.

You may encounter an error if you run Hyper-V host backup, as this is not supported with the current released version of the VSS hardware provider. For application consistent backup, take a snapshot within the VM guest.
However, snapshots auto-recovery is not required when the VM is turned off or in case of crash-consistent backup.

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