[Linux-cluster] Guidelines on Upgrades

[Robert Hayden]

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

I suspect that minor OS upgrades and errata would survive a rolling upgrade,
allowing for the RHCS to run in a mixed mode for a short period of time.
The major OS upgrades, since RH can introduce non-passive changes, may
require some ingenuity on dividing the cluster up and experiencing a small
downtime to flip from one subset to another.

I have read the RH documentation on the RHEL 4 to RHEL 5 upgrades which
indicate a full cluster downtime is needed to convert GLUM to CMAN
configuration.

Sorry if this topic has been discussed before, but I could not locate any
clear cut rules or direction from the community.

Thanks
Robert
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