Mixed PVE8/PVE9 cluster - how stable is it?

[EvertM]

Hi all,

We have a cluster of 3 PVE nodes, all currently running PVE8. I would like to upgrade them all to PVE9 with minimal downtime. This would mean we'd be running a cluster with both PVE8 & PVE9 nodes for some days.
Will this work? Is it as stable as a cluster with only PVE8 or only PVE9 nodes? We don't use anything fancy like live migration or Ceph.

 

[apoyen]

Hello,

You can do it but I recommend you to not stay for a long time in this configuration. Limit modification in your cluster until you have completed your migration.

Avoid migration from a node with PVE9 to PVE8 nodes and always use web interface with the same version the node you are administrating.

If your are using HA I think it's better to disable it during your migration (for a few days).

 

[EvertM]

Hello,

You can do it but I recommend you to not stay for a long time in this configuration. Limit modification in your cluster until you have completed your migration.

Avoid migration from a node with PVE9 to PVE8 nodes and always use web interface with the same version the node you are administrating.

If your are using HA I think it's better to disable it during your migration (for a few days).

Thank you for the fast reply
We're not migrating between nodes, and we do not use HA at the moment.

 

[skraw]

I would love to see some official statement on this question because absolutely everybody with a cluster runs into this while upgrading to pve9. Me I'd like to add a new pve9 node to an existing pve8 cluster ...
Migration from pve8 guest to pve9 node is also an important point.

 

[aaron]

What @apoyen said is correct.

In general, also within the same major version, the following applies to live migrations: old → new version should always work. new → old can work, but there might be breaking changes.

During an upgrade, you might run into errors if you use the web UI of one node to make changes on another node if the nodes run different versions.

So keep the upgrade window as short as possible and avoid modification to the cluster during that time. But a few days can be okay.

Me I'd like to add a new pve9 node to an existing pve8 cluster ...

That is not a tested scenario. It might work, though. The safer way would be to install the new node with PVE 8 if you need the additional resources right away and then do the cluster upgrade.

 

[skraw]

That is not a tested scenario. It might work, though. The safer way would be to install the new node with PVE 8 if you need the additional resources right away and then do the cluster upgrade.

We could not use pve8 because of the old zfs version included there. We incorporated a zfs volume from another setup which only worked with the zfs version of pve9. Mount was not possible with pve8.