HyperV Quiescence vs. APP

[gotsch]

Hi Guys,

we have a Server 2016 Cluster with 3 Hosts. There are 110 VMs in this Cluster, seperated in 40 VLANs. The Hosts and the Backupserver are not able to enter the VMs via Network because of the VLANs. Striktly separated. There are 97 % Microsoft OS across the VMs.

In the past (with 2012R2 Cluster) we did only HyperV Quiescence Chrash Consistent Backups of all Vms and we lived well with it. All VMs with DBs had truncated LOGs (Exchange, SQL).

Now with Veeam 9.5 Update 3 on Server 2016 I must recognize, that all Exchange LOGs - doesnt matter if it's EX 2013/2016 or OS 2012R2/2016 - have no truncated LOGs anymore. Is it a Bug? Or a feature? Am I forced to use APP in future (I wont because then I had to open Firewalls etc.)? I tested APP with one Exchange and voila, LOGs got truncated..

Does anybody see semilar behavior with HyperV Quiescence?

Patrick

[PTide]

Hi,

That is an expected behaviour, please see this article:

If you use Microsoft Hyper-V guest quiescence, Veeam Backup & Replication will quiesce the VM but will not perform application-specific actions required for proper backup and restore of VMs running highly transactional applications. Application-specific steps include the following tasks:

- Applying application-specific settings to prepare applications for VSS-aware restore at the next VM startup
- Truncating transaction logs after successful backup or replication.

Thanks

[gotsch]

Ty for your answer.

Just for clarification:

It is a change with Veeam 9.5 or with Server 2016? I only ask because it worked worked before our Upgrade --> HyperV Quiescence truncated all LOGs.

For examble: I have anopther HyperV Cluster. It's Server 2012R2 with Veeam 9.5 U3 and one VM Server 2012R2 with Excahnge 2013. Backup Job is just HyperV Quiescence --> guess what happens?! LOGs got truncated. Easily. Like it has done ever.
I have more HyperV Clusters with 2012R2, Veeam 9.5U3, but Exchange 2010... only HyperV Quiesncence, all LOGs truncated.

So I can not believe it's an expected behavior in general for Veeam and MS Server, that LOGs don't get truncated with HyperV Quiescence.

[nmdange]

Are you sure you haven't enabled Circular Logging on these Exchange servers?

[gotsch]

Yes I am sure. We use Circular Logging only für trouble shooting. So it is disabled by default in our environments.

[Mike Resseler]

Hi Patrick,

The way the backup is performed in server 2016 has changed completely against how it was done in 2012 R2. To make it very short: 2016 does not rely on the host VSS anymore. In Hyper-V 2016, you have 3 snapshot types: Application consistent, File-level consistent, Crash-consistent.

- Application consistent leverages the VSS guest framework inside.
- File-level consistent works through a filter driver (now provided by MSFT itself) and simply will take a backup, but not leverage VSS (so no truncation and so on...)
- Crash-consistent... Well, you know what that is.

When you go into Hyper-V manager, you can actually check what the default is when you create a checkpoint (I cannot say snapshot anymore in the Hyper-V world ). Have a look at your servers what the default action is. Open the settings for a exchange server VM, and have a look at Management/ Checkpoints. See what the default action is (normally production with a failback to standard if that doesn't work.) As a test I would "deny" the failback (uncheck the box) and (outside of Veeam) create a production checkpoint. If that works, make sure that you merge the AVHDX and VHDX (don't forget to do that so you don't loose data ). Now have a look inside the VM whether or not you have log truncation. My gut feeling says NO . Look at VSS in event viewer and see what it tells you.

Mike

[gotsch]

So I finally had some time to test other Hosts with 2016 HyperV and Exchange, but with Exchange installed on a 2016 VM

Guess what..

Log Truncating works perfectly with HyperV Quiesncence on (and AAP off) on HyperV 2016 and VM 2016... so for me this is a bug like the failling Backup of DCs on 2012R2 VMs on 2016 Host (which finally got fixed after 8 month...) ... this sh*t is getting on my nervs for months now... argh.

[gotsch]

So can I assume that Veeam Stuff is not aware of that a Server VM 2012R2 with Exchange on a 2016 Host will NOT truncate LOGs with HyperV Quiescence?

[foggy]

Hi Patrick, Veeam staff is aware, but the reason of this behavior lies in the fact that in this case (Windows 2012R2 or older guest on a Windows 2016 host, Hyper-V guest quiescence) Hyper-V host doesn't inform the guest VSS Service when the backup is complete, which makes logs truncation impossible.