Are the backups "windows active directory aware" ?

Jan 8, 2021
Hi guys,

So the question is: are the incremental backups "windows active directory aware" - customer had asked us this question today because apparently there's an old issue with AD, that caused USN rollback errors when a virtual active directory server was restored from an image and we are clueless.

Thanks in advance,


Proxmox Staff Member
Staff member
Jul 28, 2015
South Tyrol/Italy

The deduplication/incremental-send layer is one below QEMU backup itself and provided by PBS, so they're as aware as an old-style vzdump backup.

For guaranteeing a clean state of the guest during backup one would either use stop-mode, with its disadvantage of resulting in a downtime. Alternatively, to avoid downtime, one could set up the QEMU Guest Agent inside the VM and then set the respective "enable QGA" option for the VM in Proxmox VE, as then a filesystem freeze is done from inside the guest using the guest OS safe APIs (VSS in Windows) before snapshotting the disk state for the backup, which is enough for most software to have a clean state.

Having separate AD specific backups could be still reasonable, also restore tests, which need to be done a bit more careful with things like AD, e.g., with network cut-off or isolated for the restore test VM to avoid causing possible havoc of multiple AD/DC instances in the production network.


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