[Beowulf] How to Diagnose Cause of Cluster Ethernet Errors?

Jon Forrest jlforrest at berkeley.edu
Sun Apr 1 09:58:49 PDT 2007

Douglas Eadline wrote:

> <Soapbox>
> I am constantly amazed at how many people buy the
> latest and greatest node hardware and then connect
> them with a sub-optimal switch (or cheap cables), thus reducing
> the effective performance of the nodes (for parallel
> applications). Kind "penny wise and pound foolish" as they say.
> </Soapbox>

I sincerely appreciate all the comments about my problem. I will reply
to them in due time. However, I'd like to comment on this, which
admittedly is off-topic from my original posting.

I don't disagree with what you're saying. The problem is how
to recognize "sub-optimal" equipment. For example, I see
three tiers in ethernet switching hardware:

1) The low-end, e.g. Netgear, Linksys, D-link, ...

2) The mid-end, e.g. HP Procurve, Dell, SMC, ...

3) The high-end, e.g. Cisco, Foundry, ...

What I, as a system manager, not as an Electrical Engineer,
have trouble understanding, is what the true differences
are between these levels, and, at one level, between
the various vendors.

These days I suspect that many of the vendors are using
ASICs made by other chip companies, and the many vendors
use the same ASICs. Assuming that's true, where's the
added value that justifies the cost differences? Sometimes
the value is in the "management" abilities of a device.
I don't deny this can be a major selling point in a
large enterprise environment, but in a 30-node cluster,
or a small LAN, it's hard to justify paying for this.

In terms of ethernet performance, once a device
can handle wirespeed communication on all ports,
where's the added value that justifies the added
cost? I'm looking for empirical answers, which
aren't always easy to find, and sometimes to understand.

In the case of my cluser, it was configured and purchased
before I got here, so I had nothing to do with choosing
its components but I have to admit that I'm not
sure what I would have done differently.


Jon Forrest
Unix Computing Support
College of Chemistry
173 Tan Hall
University of California Berkeley
Berkeley, CA
jlforrest at berkeley.edu

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