Snapshot / Suspend / Stop?

[enoch85]

Didn't find any info in the documentation, maybe I missed it, but I'm simply wondering what the difference is?
I come from Veeam where it snapshots the VM and then sync that to the backup drive/disk. Restore has never been an issue before, but now I've read online that you need to stop the VM for it to become a full recoverable clone with all the settings intact, so which is it?

I use ZFS for everything, so I got me thinking that maybe PBS is so smart that it utilizes ZFS for the snapshot, and in that case I'm not worried. I mean, that would be the perfect snapshot with everything intact.

Thanks!

 

[Dunuin]

Didn't find any info in the documentation, maybe I missed it, but I'm simply wondering what the difference is?

https://pve.proxmox.com/wiki/Backup_and_Restore#_backup_modes

I use ZFS for everything, so I got me thinking that maybe PBS is so smart that it utilizes ZFS for the snapshot, and in that case I'm not worried. I mean, that would be the perfect snapshot with everything intact.

Make sure you got the QEMU guest agent installed everywhere. ZFS snapshots won't ensure data integrity when the guests caches aren't flushed (by PVE triggering fsfreeze) before doing the snapshot. And even then restoring a snapshot mode backup is like booting an guest after an power outage as all processes will crash with data in RAM lost (unless you also dump the RAM, but that only works for snapshots, not for snapshot mode backups).

 

[poetry]

One thing I am also wondering is can you make a snapshot without any interruption to the VM OS. Example I have a VM Windows Server 2022 terminal server with 100 active users on the terminal can I make a snapshot without losing connection to terminal like will the users notice the snapshot creation? Will they lose connection to the VM and for how long? This is not a problem on vmware how it's on PVE?

 

[fiona]

Hi,

One thing I am also wondering is can you make a snapshot without any interruption to the VM OS. Example I have a VM Windows Server 2022 terminal server with 100 active users on the terminal can I make a snapshot without losing connection to terminal like will the users notice the snapshot creation? Will they lose connection to the VM and for how long? This is not a problem on vmware how it's on PVE?

with snapshot mode, there is no interruption for VMs. The snapshot is taken on QEMU's block layer by introducing a new block node. When using the agent, the filesystem is forzen during the creation of the block node (and if using PBS during connection to the server), but those shouldn't take long. During the backup, if you have IO to lots of different places it might get bottle-necked by the backup speed. But you shouldn't experience real downtime of the guest.

 

[poetry]

Hi,

with snapshot mode, there is no interruption for VMs. The snapshot is taken on QEMU's block layer by introducing a new block node. When using the agent, the filesystem is forzen during the creation of the block node (and if using PBS during connection to the server), but those shouldn't take long. During the backup, if you have IO to lots of different places it might get bottle-necked by the backup speed. But you shouldn't experience real downtime of the guest.

Thank you for this. This is helpful to keep in mind.

 

[macson]

I'm not sure if this brings totally clarity for me, I have a Windows Server machine running as a VM, it it safe to use snapshot backups or would it be recommended to suspend or stop before? Anyone that have had problems with just using snapshot mode backups?

 

[Noah0302]

I'm not sure if this brings totally clarity for me, I have a Windows Server machine running as a VM, it it safe to use snapshot backups or would it be recommended to suspend or stop before? Anyone that have had problems with just using snapshot mode backups?

If you have the Windows VirtIO-Driver installed, there should be no Issue with using Snapshot as a Backup-Method, as @fiona metioned above:

with snapshot mode, there is no interruption for VMs. The snapshot is taken on QEMU's block layer by introducing a new block node. When using the agent, the filesystem is forzen during the creation of the block node (and if using PBS during connection to the server), but those shouldn't take long. During the backup, if you have IO to lots of different places it might get bottle-necked by the backup speed. But you shouldn't experience real downtime of the guest.

Ive been using Snapshot Backups for Years without Problems, with the VirtIO-Driver installed, mind you!