[Pacemaker] Where to install applications

[Florian Haas]

On Fri, Dec 2, 2011 at 5:35 PM, Charles DeVoe <scarecrow_57 at yahoo.com> wrote:
>
> We are building a 4 node active/active cluster, which I believe is the same as High Performance.

Not quite. That's still an HA cluster with some scale-out capability.
HPC is a slightly different ballgame.

>  The Cluster has a SAN formatted with GFS2.  The discussion is whether to install the applications on the shared drive and point each machine to that install point or install the applications locally.

Your call, really.

Slapping all applications onto the shared storage means that every
time you update that piece of software, you essentially have to
restart everything all at once -- but only once. So, for updates
you'll normally have downtime. If everything goes nicely, you're back
up very quickly. If something breaks, you're down for some time.

Putting just the data on shared storage, and the applications on
individual nodes, means you're capable of "rolling" upgrades where you
update your software node by node -- but then again, you have to do it
on every node. If everything works on the first try, you'll normally
take a bit longer than in the approach explained above. If something
breaks on the upgrade of your first node, well, you shut it down, go
back to square one, find and fix the root cause, while three others
continue to hum along.

I for one much prefer the second approach.

Cheers,
Florian

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