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

Prentice Bisbal prentice at ias.edu
Tue Sep 23 08:36:38 EDT 2008



Gerry Creager wrote:
> Eric Thibodeau wrote:
>> Prentice Bisbal wrote:
>>> The more services you run on your cluster node (gmond, sendmail, etc.)
>>> the less performance is available for number crunching, but at the same
>>> time, administration difficulty increases. For example, if you turn off
>>> postfix/sendmail, you'll no longer get automated e-mails from your
>>> system to alert you to a problem.
>>>
>>> My question is this: how extreme do you go in disabling non-essential
>>> services on your cluster nodes? Do you turn off *everything* that's not
>>> absolutely necessary, do you leave somethings running to make
>>> administration easier?
>>>   
>> Everything is turned off and, most of the time, a quick glance at
>> ganglia brings out problems. Simple scripts can be built to perform
>> cyclic checks on the nodes and would be less disruptive IMHO.
>>> I'm curious to see how everyone else has their cluster(s) configured.
>>>   
>> The only actual research I found on OS interference impacting HPC
>> computing is titled "A measurement and simulation methodology for
>> parallel computing performance studies" by Matthew Joseph Sottile. I
>> would be curious to know if anyone else has dipped into the subject
>> and come up with conclusive results on the subject.
> 
> As a slightly OT question: I've recently heard it posited that ganglia
> induces severe communications overhead ("It's chatty") and thus
> shouldn't be used.  What's the conventional wisdom thereof?

I believe it. I remember debugging a ganglia communication problem once,
and saw LOTS of traffic with tcpdump. I would imagine that gmond
produces a decent amount of load on the node everytime it polls the
system. I could be wrong on that last part, since I don't understand how
it works internally.

If ganglia produces a lot of traffic and some overhead, is it really
that bad to leave postfix/sendmail running so I can receive e-mail
system e-mails?

-- 
Prentice
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