How much does constant backing up to PBS affect the VM?

[ProxNoel]

Hi!

I have a main proxmox node with 5-10 VMs.
I also have a remote proxmox node with PBS installed as a VM.
I want to create some kind of disaster recovery site with this remote proxmox node.

My plan is to take backup of the VMs every minute and send to PBS. Most of the VMs are static so storage is a non issue.

But my question is if the constant backing up will reduce performance? Or is there more consequences I have missed?

 

[UdoB]

But my question is if the constant backing up will reduce performance?

Of course the answer depends completely on your application. But one minute interval is really, really short - actually the absolutely shortest theoretically possible. I would recommend to work with snapshots for such a high frequency and run backup "only" every 15 minutes or so...

Possibly correct answer: no. After the first backup the "dirty bitmap" is valid and only actually changed data is read from disk (or cache) and then transferred to PBS. For "normal" VMs this is totally painless.

Other answer: yes, if you run busy databases, for example.

Final answer: just test it! And please tell us your findings


Disclaimer: I've never tried to run backups with such a short interval...

 

[ProxNoel]

Thank you for your reply @UdoB!
I completely agree with you that there is many many elements that are in the mix.

The reasoning is to use backups instead of snapshots are that I want to save the data in the remote site and the main node and the remote node use different storage formats (not ZFS). I haven't found any process to make use of snapshots with this configuration.

So when using pbs I get the incremental backup function and as long as the VM is not restarted or changed too much the backup should just take seconds or less.

My plan is to use qemu-agents on all the VMs so they can utilize guest-fsfreeze-freeze and guest-fsfreeze-thaw. I cannot find "how much" this will improve the continous backup. If anyone have some experience or information I would be very happy if you let me know!