Troubleshooting on Microsoft Hyper-V VSS Writer. The writer experienced a partial failure

We have this issue on our Windows Backup issue (wbadmin) from one of our Hyper-V server. We haven't got any backup issues till we applied one of the Windows updates.

Machine environment:

• Windows Server 2012 R2

• The Hyper-V and VM backups is pointing to USB portable device.

• USB portable device is apart of Disk 2 Basic appearing in Disk Management (Disk 0: primary physical disk partition, Disk 1: Mini disk storage - 18GB)

Error Detail:

Microsoft Hyper-V VSS Writer The writer experienced a partial failure. Check the component level error state for more information. (0x80042336) Unspecified error (0x80004005)

What we did so far:

• Rebooting the machines few time >>> No luck

• Apply the Autoamount command on DISKPART >>> No luck

Any ideas?

We managed to solve this issue. After looking intensively on the Event Logs under Applications and Service Logs / Microsoft / Windows / Hyper-V-XXXXXX and we found the permission issue - General access denied error (0x80070005). It's missing the "NT VIRTUAL MACHINE[VM-GUID]" on our Virtual Machines directory.

Apply this ICacls and it worked nicely - the backup is working ok now.

D:\Virtual Machines>icacls "D:\Virtual Machines\xxAUxxxSQD01-VM" /T /grant "NT VIRTUAL MACHINE\C2C11601-0A27-4E61-AF82-34D3C866AFDA":(F)