Newbie

[Bohn Christopher A Capt AFRL/IFSD]

> -----Original Message-----
> From: Niels R. Walet [mailto:mccsnrw@dirac.phy.umist.ac.uk]
> Sent: Thursday, June 17, 1999 4:35 AM
> To: dan@quetzalcoatl.com
[...]
> > Third: A less interesting questions unless you want to
> > take an easy jab at me. {:-) I understand the differences
> > between the switches and hubs, but has anyone benchmarked
> > the performance degredation when using a Hub? I do not
> > think I will cheap out here, but I was just interested
> > in if the bottle necks on diskless clients would be in 
> > communicating with the server, or in the hub/switch. 
> 
> This is one for the FAQ: It really depends on your application.
> Since you have diskless clients, you will(?) both have NFS traffic
> and message passing at the same time, so you might also choose
> to double the number of NICs. Benchmarks are only useful for
> your application. (But prices are so low that I see no reason
> for buying a hub rather than a switch....).
 

Let me emphatically second this -- it very very much depends on the
application.  When we moved from a hub to a switch, we did some testing with
basic stuff such as latency, etc.  We found (as expected) the latency in the
switch was higher, but for two of the four of us, the performance with our
applications was significantly better because of the degree of  interprocess
communication, and the other two were just much better.  Mainly what we saw
was that (for our apps) while the mean run time decreased enough to make us
happy, the variance decreased dramatically because the randomness introduced
by packet collisions had almost (but not entirely) disappeared.

Take care,
cb
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