VM Backup with snapshot mode

[trilljester]

Hi,

This is more of a quick and probably easily answered question. When I start a backup of a VM in snapshot mode, it freezes the filesystem, makes a snapshot, and then thaws the filesystem and writes a backup of the VM to a file. Is that correct? Would files changing during that backup would not appear in the final backup image, correct? Thanks!

 

[t.lamprecht]

Hi,

This is more of a quick and probably easily answered question. When I start a backup of a VM in snapshot mode, it freezes the filesystem, makes a snapshot, and then thaws the filesystem and writes a backup of the VM to a file. Is that correct?

Yes, where snapshot is done at QEMU's block level with our implementation that syncs all block devices (disks) consistently.
Note that freeze/thaw requires the guest to have the QEMU guest agent installed and the respective VM option to be enabled.

https://pve.proxmox.com/pve-docs/chapter-vzdump.html#_backup_modes (check also out the from there linked technical overview for more details)

Would files changing during that backup would not appear in the final backup image, correct?

All changes happened before the freeze will be visible in the backup, all changes after the thaw won't.