ZFS snapshot as vm image backup

So i've got my vm hdd image on a zfs volume, what would be the problems, if any, of using zfs snapshots to take a backup? The snapshot would be saved to file or remote zfs.

I'm hoping the snapshot of the running machine would be the equivalent of the machine not shutting down properly, which to me, is not that risky for this data.

 

https://en.wikipedia.org/wiki/Quiesce

 

That's pretty much it. How reliable that is depends on how busy the VM is, and the software it uses.

You can minimise the impact by running things like "sync" under Linux, or an equivalent under Windows (forcing a flush of all caches to disk) before the snapshot runs, although that can be a bit tricky as you need to do it inside the VM (perhaps an SSH-key based one-shot command that does it?).

 

Is not a good practice, for the snapshot to be any good the VM must be in a static state, but more importantly all updates and actions be in a completed state. Pausing the VM (Xen suspend, KVM suspend, VMware pause, HyperV NFI) then snapshot will guarantee recovery.

BUT, this does not guarantee that any application running on the server is in a recoverable state, especially DB's, so you will need to stop or pause these so they are in a recoverable state first.

What is the use case?