How to safely enable KRBD in a 5 node production environment running 7.4.19

[john.gaspode]

I’m running a 5-node Proxmox cluster on version 7.4.19 with two storage pools: one on spindle drives and the other on SSDs. Both pools host live VMs, but performance is slower than expected, with high IOWait states.

I’ve read that enabling KRBD can improve performance, but I haven’t found clear guidance on how to safely enable it.

Currently, I’m in the process of updating the cluster to Proxmox 8 but have paused after upgrading all nodes to version 7.4.19. The Proxmox OS itself is installed on spindle drives.

Here are my questions:

What happens when I enable the KRBD option for the pools?
Will live VMs need to be restarted to apply the changes?
Do the host machines require a restart after enabling KRBD?
Should I shut down all VMs before enabling the option?
Would it be better to complete the upgrade to Proxmox 8 before enabling KRBD?

Thank you for your help!

 

[Maximiliano]

Hello,

What happens when I enable the KRBD option for the pools?

You will use the RBD kernel module instead of librbd. In certain setup/workloads KRBD could offer better performance.

Will live VMs need to be restarted to apply the changes?

It depends on what do you mean by a reboot. To be sure, I would recommend to *completely* shut down the VM and start it again.

Do the host machines require a restart after enabling KRBD?

No.

Should I shut down all VMs before enabling the option?

No.

Would it be better to complete the upgrade to Proxmox 8 before enabling KRBD?

It should not really matter whether your upgrade for the purpose of enabling KRBD. However, Proxmox VE 7 is End-of-Life [1] so yes, I would recommend to update it regardless.

You can go to your storage settings at Datacenter->Storage->{RBD storage} and check the KRBD checkbox in the dialog to enable it. As mentioned you will need to cold-reboot the guests for it to take into effect.

[1] https://forum.proxmox.com/threads/proxmox-ve-support-lifecycle.35755/

 

[john.gaspode]

Thank you for the reply,

We enabled KRBD and it seems to have helped.

 

[tomatoschewps]

Hi,
Thanks @john.gaspode for the question, it was a topic for me last week. I had no urgency so for the moment I hadn't done anything until I found the info ^^

Instead of cold-reboot, if we live migrate VMs to another host (and eventually migrate back after) will it be sufficient ?