Upgrade Proxmox Cluster from 8.4 to 9 – Can I migrate VMs back to the upgraded node before finishing all nodes?

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torbho

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May 8, 2025
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Hi everyone,

I’m running a 3-node Proxmox VE HA-cluster (currently 8.4.12) and I’m planning to upgrade to version 9.

My question is:
  • After upgrading the first node to Proxmox 9, is it safe to migrate VMs back to this upgraded node while the other two nodes are still running 8.4?
  • Or do I have to shut down the VMs until all nodes are on the same major version?
I’d like to minimize downtime and I want to make sure I don’t run into cluster or migration issues due to mixed versions.

I couldn't find anything to this specific scenario in the documentation.
Thanks for clarifying!
 
Yes Proxmox makes sure that you can always migrate to a newer node (but not back from the new node to an older one). Livemigration is no problem, have fun!
 
Thanks a lot for the clarification regarding migration direction (8.4 → 9 is fine, but not back). That helps a lot!

One more thing I came across: I noticed that Proxmox 8.4 and 9 ship with different Ceph versions. My virtual machines do use Ceph.
Does this cause any issues in a mixed cluster during the upgrade phase?
 
jsterr said:
Yes Proxmox makes sure that you can always migrate to a newer node (but not back from the new node to an older one). Livemigration is no problem, have fun!
Click to expand...
Thank you!

pvps1 said:
follow the upgrade instructions strictly (!)
ceph upgrade is always mentioned as a special step.

worked like charm for the last decade IF you follow official howto
Click to expand...
Thank you, too.

I will try the upgrade in some days. *fingers crossed*
 
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