Mixing release versions in a cluster?

[lejeczek]

Hi guys.

Might be trivial yet a novice failed to find an answer(in the docs) - is it possible (even if not "formally" approved/advised) to add nodes with different PVE version to an already existing cluster?
Naturally I'm thinking - 7.x existing cluster would get 8.x node added/introduced.
If possible what are the "gotchas" if any? Perhaps such a scenario is already documented somewhere?

many thanks, L.

 

[aaron]

That is not something we test against. The only time where it is okay to have mixed versions in a cluster is during the upgrade procedure.

When it comes to (live) migrations of guests between nodes keep the following in mind: migrating from an older PVE version to a newer one should always work, but from a newer to an older one might not work. This is also true within minor versions of the same major release.

Therefore, if you are about to add a new node to the cluster, install the same major version, and ideally, you also update the cluster first to the latest version of that major release so that all nodes can be on the exact same version.

 

[lejeczek]

@aaron Thanks. I've only started looking at Proxmox so that must be why it defeats me - what I'd think was simple logic, namely:
If an upgrade between major versions is possible with "zero" downtime - which I'd imagine must be with solutions such a Proxmox, the aim must be to be capable of that - then upgrading cluster must mean: a node at the time - and if that is true then....