Recently when installing Veeam Availability Suite 9.0 into a clients site with Cluster Hyper-V, we ran into a problem that took us a little time to resolve.

In the spirit of sharing knowledge, I thought I would share our findings in the hope that it will assist someone else that may experience this issue.

We had attached some iSCSI storage to the Hyper-V cluster and configured this using the Failover Cluster Manager confirming that we could read and write to the storage with no apparent issues.

We then created a number of test backup jobs within VEEAM and attempted to perform an Application aware backup and we were presented with the following error:

Writer ‘Microsoft Hyper-V VSS Writer’ is failed at ‘VSS_WS_FAILED_AT_PREPARE_SNAPSHOT’


Further investigation did not turn up any useful information and a Support Case was logged with VEEAM who requested logs from the Hyper-V Servers and VEEAM Server, and these resulted in VEEAM Support pointing us to the following errors:

  • A VSS writer has rejected an event with error 0x800423f4, The writer experienced a non-transient error.  If the backup process is retried, the error is likely to reoccur.
    . Changes that the writer made to the writer components while handling the event will not be available to the requester. Check the event log for related events from the application hosting the VSS writer.Operation:
    PrepareForSnapshot Event

Execution Context: Writer
Writer Class Id: {66841cd4-6ded-4f4b-8f17-fd23f8ddc3de}
Writer Name: Microsoft Hyper-V VSS Writer
Writer Instance ID: {c2f0023d-eb41-4181-8c5e-52e873d61825}
Command Line: C:\Windows\system32\vmms.exe
Process ID: 4108

Timeout waiting for iSCSI persistently bound volumes. If there are any services or applications that use information stored on these volumes then they may not start or may report errors.

Status 0x00001069 determining that device interface \\?\{8e7bd593-6e6c-4c52-86a6-77175494dd8e}#MsVhdHba#1&3030e83&0&01#{2accfe60-c130-11d2-b082-00a0c91efb8b}does not support iSCSI WMI interfaces. If this device is not an iSCSI HBA then this error can be ignored.

I would ask you, first of all, restart the service Hyper-V Virtual Machine Management on the host HV-1-2. If after that the backup job fails, please reboot the HV-1-2 host.

Could you also specify if you have disks which connected via iSCSI?

Nothing that was suggested gave us any true indication as to the problem, because iSCSI seemed to be reading a writing fine, leading us to believe that there was not any problem with the iSCSI side of things.

We then decided to try to create a Checkpoint (Microsoft’s new name for Snapshot) from within the Hyper-V Manager and to our surprise this also failed with the following error:

“cannot create the storage required for the checkpoint using disk general access denied error(0x80070005)”

A search for this error, lead us to a Veritas Support Article that indicated that VHDX files should not be located in the root of the CSV (Cluster Shared Volume)

Upon further inspection we discovered that the VEEAM Repository Disks that we had created were in fact located in the root of the iSCSI CSV and it was then a simple process of shutting down the VEEAM Server and relocating the VHDX files into a suitable sub-directory as follows:


Then it was a simple case of updating the VM settings with the new disk locations.

We then restarted the VEEAM Server and lo and behold, we were able to create a Checkpoint within Hyper-V and the VEEAM backups also worked fine.