This week I was evaluating Altaro VM-Backup because I read that they had released version 6, which now supports backing up virtual machine running on the VMware hyper visor. Apart from that, I needed to deploy Altaro VM-Backup to a customer of ours for whom we configured a Hyper-V Failover Cluster.For this reason I first tested backing up my Hyper-V lab environment.

My Hyper-V lab consists of two Hyper-V nodes with the Failover Cluster role installed, connected to an Equallogic PS6000 SAN. I have 1 witness virtual disk and 1 CSV virtual disk presented to both Hosts.I also Have a backup server which has Altaro VM-Backup installed and is used as the storage location.

Installing the application was very simple. The wizard was easy to follow and intuitive.

After Adding my hosts and storage location, I configured my backup and ran it. Upon execution I wanted to see if the Hardware VSS provider would be used to offload the snapshot creation process to the SAN. Since I was not able to select if the backup should use the hardware of software VSS provider, I assumed that the application will use the software provider. In my case that is what happened.

I contacted Altaro support to see if what I wanted to do was possible. They informed me that, if available, the application will try to use the hardware provider to create the snapshot. As in my case this didn’t work, support suggested that I should use the VssOverrideProviders.txt file to force the application to use the relevant vss provider for the volume.

Each line in the file will contain the volume identifier | the identifier of the vss provider to be used

For example: \\?\Volume{90400436-b19d-4e77-8d9a-34f8db5be5bf}\|d4689bdf-7b60-4f6e-9afb-2d13c01b12ea

The volume identifier can be obtained by opening an elevated command prompt on one of the Hyper-V hosts and executing the “mountvol” command.

The output will contain something similar to:

mountvol output

Then run the command “vssadmin list providers” which will output something similar to :

vssadmin list providers output

You need to locate the volume and vss provider ids, marked in red, and populate the VssOverrideProviders.txt file with them.

Now all you need to do is copy the txt file to the below location on each Hyper-V host which has the CSV virtual disk attached to it.


The overrides folder may need to be created if it does not already exist.

Once this was done, I ran a backup and could see that the Hardware VSS provider was used because a snapshot was created on the Equallogic SAN.

Snapshot created on SAN

Once the backup is complete, the snapshot was deleted from the SAN.

The utilisation of Hardware VSS Providers will allow the Host to offload the snapshot creation to the SAN.


In order to have this functionality working, you need to have all the components in place. In the case of an Equallogic SAN, you will need to install the Host Integration Tools on the Hyper-V Hosts and setup the VSS/VDS account on the SAN. I have documented the process here.

I would like to thank Altaro Support for the quick support provided with this and for allowing me to document it.

If you have some feedback to add, please leave a comment.



By Brian Farrugia

I am the author of More info can be found on the about page.

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