[ovirt-users] Cluster compatibility version and major upgrades

[Chris Adams]

Hello again, still working on my upgrade from 3.5...

I'm trying to understand the cluster compatibility version setting and
how that applies to major upgrades.  Do I have to always raise the
compatibility version when I do a major upgrade?  In other words, when I
upgrade from 3.5 to 3.6, do I need to raise it to 3.6 before I upgrade
to 4.0 (and then again raise it 4.0 before upgrading to 4.1)?

It looks like the 3.6->4.0 EL6->EL7 migration requires the cluster
compatibility level to be at 3.6 (if I'm reading things right).

It appears that when I upgrade to 3.6, I will have to stop all running
VMs to raise the compatibility version (and I found an open bug about
whether that's possible with the hosted engine).  It sounds like with
4.0, the VMs can be flagged for compatibility and I can reboot them
individually.  I have over 80 VMs, many behind a load balancer (for HA
and load sharing), but taking them all down will obviously still
interrupt service for a while.

Is there a safe way around that?

I saw someone mention they partitioned their servers and made a new
cluster (with the new version), and migrated VMs from cluster to
cluster.  Can I do live migrations in that case?  How do I get the
hosted engine from one cluster to another (especially with starting at
3.5)?

-- 
Chris Adams <cma at cmadams.net>