Re: A proposal for a General Clustering Framework

[Alan Robertson <alanr@unix.sh>]

Peter Badovinatz wrote:
> 

[snip]

> Depends...  We could push customers who really cared about strict HA to avoid
> version heterogeneity except during actual node-by-node upgrade.  It was
> customers who were more oriented to cluster file system - where we still needed
> (a bit looser form of) HA and failover but they could be up to 500 node
> clusters - that we had no choice but to be very flexible as to supporting
> multiple versions across nodes because upgrading 500 nodes a few at a time
> takes a long time, and unlike more controlled HA clusters the workload was
> quite varied so many more things to upgrade/test/migrate.
> 
> The better choice is to be sure the framework lets you handle multiple active
> version levels from the beginning, and you work to minimise their use by decree
> (as above) or by only supporting some limited number of levels (N and N+1 or
> N+2.)

The conclusions I would draw from this are:

	The real world is ugly.

	Technology had better be equipped to deal with it.

	Sensible policies help you keep out of trouble.

	Policies are not guarantees.

I view these as all perfectly consistent with what I said before.

	-- Alan Robertson
	   alanr@unix.sh

Linux-cluster: generic cluster infrastructure for Linux
Archive:       http://mail.nl.linux.org/linux-cluster/