[Beowulf] What services do you run on your cluster nodes?

Perry E. Metzger perry at piermont.com
Tue Sep 23 09:15:18 EDT 2008


Ashley Pittman <apittman at concurrent-thinking.com> writes:
> Note that it's not just the "OS" fluff which causes problems and turning
> things off doesn't get you anything like 100% of the way there, some
> deamons have to run (your job scheduler) so all you can do it tune them
> or re-code them to use less CPU and some kernel versions are pretty bad,
> one version of Red-Hat was effectively un-usable on clusters because of
> kscand.

To agree with you and to expand a bit:

In theory, daemons should not be an issue. With a properly written
real time scheduler and proper interrupt management, one can
reasonably guarantee maximum latencies.

However, in practice:

1) PC hardware is incapable of guaranteeing very tight latencies, full
   stop. I've mentioned SM mode, and that's only one of the issues you
   face.
2) Most operating systems are not designed for true real time
   performance. They are built to maximize throughput, not to minimize
   latency. Linux is no exception.


Perry
-- 
Perry E. Metzger		perry at piermont.com
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