[Linux-cluster] Guidelines on Upgrades

[Mikko Partio]

On Sat, Aug 14, 2010 at 12:11 AM, Robert Hayden <rhayden.public at gmail.com>wrote:

> Looking for guidelines on when RHCS components can be upgraded in a rolling
> fashion and when it is best to simply take a full cluster downtime.  I am
> looking at 2-6 node clusters with each node providing a unique set of
> functions along with common functions.  Each node has a dedicated failover
> node(s).
>
> A couple of examples:
> Minor OS upgrades, e.g. RHEL 5.3 to RHEL 5.5
> Major OS upgrades, e.g. RHEL 5.x to RHEL 6.x
> Errata for key cluster component, e.g. openais, cman, etc, without kernel
> updates
>

My understanding is that major upgrade require rebuilding the cluster from
scratch, ie. no upgrade is possible. And with minor upgrades, I've tried
doing rolling upgrades and sometime they do work and sometime don't. The
problem is that you don't know which upgrades will work, so my current
approach is just to upgrade the whole cluster at a time. Sure, requires some
downtime (5-15 minutes) but that's better than having a freezed cluster
requiring hours of work to get back online.

Just my $0.02.

Regards

Mikko
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