Doing a bit more hunting it seems like if we could get Arcserve to use the nolock option then that would likely solve the problem, but there's nowhere to add any options and the Arcserve Proxy itself uses the Windows NFS client behind the scenes.
Right now we've worked around the problem by creating a separate, read-only SMB share pointing to the same location and using that for Arcserve instead. Our only concern now is what could happen if XO starts a job while Arcserve is still doing its own backup. 🤔
If you're having trouble with the NFS locking mechanism, and you would like to use the "NET USE" command, or the [WNetAddConnection] function to mount a NFS share without locking, there's an undocumented registry entry hidden in the NFSNP.DLL:
"HKLM\Software\Microsoft\Client for NFS\CurrentVersion\Users\Default\Mount" REG_DWORD "Locking"
If the value is "0x0" then locking will be disabled globally.
If the value is "0x1" then locking will ben enabled globally.
To get assistance on XOA, since you have support, it's better to go with our support ticket system. This way, you can be sure to have an answer with direct developer access in a guaranteed amount of time. Please open a ticket here: https://support.vates.fr/#/tickets
XOA isn't dealing on what's inside on the VM: it's an hypervisor-level agentless backup solution. As soon you create the ticket, we'll take a more in-depth look about details (what kind of backup are you using? Delta or full etc.) and also if there anything special we could do at our level.