However, this VSS timeout error may occur on hosts without Hyper-V as well.
Try the following options to fix VSS_E_FLUSH_WRITES_TIMEOUT:
Repair Strategy #1
Using the registry editor, "HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\SPP" - If need be, create a new registry value of type DWORD with name "CreateTimeout" - Change value to 12000000(2*10*60*1000 = 20 mins) in decimal
The above should increase the VSS timeout to 20 mins
Repair Strategy #2
Check using VSSUIRUN.EXE or vssadmin list shadows whether there are any VSS shadows on the system.
If you aren’t using Windows Server Backup or some other backup software that relies on VSS shadows, go ahead and delete all of them using
vssadmin delete shadows /all
Repair Strategy #3
Check fragmentation levels, free RAM (1GB minimum), and free disk space (at least 10GB).
If you are backing up virtual machines, check inside the VMs in the Event Viewer for more error details.
Increase RAM and free disk space and test again.
Repair Strategy #4
Several types of applications make VSS timeout errors more likely: Some antivirus software may create an incompatibility. Try uninstalling it (not just switching off real-time scanning). In addition, make sure no defragmentation, antivirus scans, or any other heavy hard drive activity is taking place when initiating the backup.
Recommended Step In Addition to Above Steps
VssDiag should be able to find errors leading to VSS_E_FLUSH_WRITES_TIMEOUT.