Thanks Michal,

Your reply somehow answer to my question, but I still have some bits of fuzziness

Hosted engine VM upgrade itself is almost clear (maintenance, db backup, reformat, reinstall, db import).

However:

1. Inter-cluster migration is somehow unsupported. Should we worried about moving VM from EL6 cluster to EL7? You know... different vdsm etc.... is ovirt migration feature atomic and reversible (if something goes wrong during the process)?

2. More important: the only Ovirt version that supports both EL6.6 and EL7.1 is 3.53. my real question is: what happen as soon as I finish upgrade of my ovirt to version 3.54 (or 3.55) while running HOSTS on EL6.6?

I mean, there will be a point in time when a version mismatch/overlap will be unavoidable.

For example: how people should correctly jump from version 3.53 (EL6.6) to 3.54 (EL6.7)?

Ovirt team should support at least one or two previous version to support overlaps...

Thanks

AG

From: Michal Skrivanek [mailto:michal.skrivanek@redhat.com]
Sent: Friday, October 09, 2015 1:33 PM
To: Andrea Ghelardi
Cc: users (users@ovirt.org); Simone Tiraboschi
Subject: Re: [ovirt-users] upgrade path from Ovirt 3.5x to 3.6x

nono, the upgrade is live and all your VMs can keep humming. But there are manual steps involved:

Simone can probably update about Hosted Engine which would be somewhat special, but at least for regular VMs you can currently use:

1) create a new cluster with same settings as your existing cluster

2) remove one host from the old cluster (the one to be upgraded/reinstalled to EL7). While moving the host to maintenance your VMs will be migrated to other EL6 hosts in that cluster (make sure you have enough capacity to do that beforehand, of course:)

3) upgrade/reinstall the host with EL7. If youdon't have anything custom on the host reinstallation might be the best option

4) add it to the new cluster, installing/deploying it via UI, then it should come up - this is your EL7-based cluster now

5) manually migrate (Migrate To button) some of your VMs from the old cluster to the new one (there's an advanced section in the dialog, allowing you cross-cluster migrations

6) repeat until all your hosts and VMs are on EL7-based cluster, then you can decommission it, and perhaps rename the cluster back to its original name

Thanks,

michal