[Beowulf] Re: switching capacity terminology confusion

Gerry Creager gerry.creager at tamu.edu
Wed Sep 16 12:28:17 EDT 2009


Greg Lindahl wrote:
> On Mon, Sep 14, 2009 at 05:52:07PM -0500, Rahul Nabar wrote:
> 
>> "Forwarding Rate 131 Mpps"  How does that tie in to the big picture?
> 
> Most layer 3 devices are not capable of forwarding full line-rate
> traffic of tiny packets. You should go hunt down a lab report on
> switch testing to see these kinds of details discussed.

A couple of vendors went after the Really Tiny Packet market some time 
back, among them Anritsu. Fujitsu resorbed Anritsu's switch-making 
capabilities, so it you want a real good idea of good small packet 
performance peruse the specs on the Fujitsu switches.

The guiding document on packet switching is (or was) RFC2544.

In looking at the Force10 S50 vs the Dell switch, I'd go with the 
increased performance specs in the Force10, even though the S50 isn't 
really Force10 silicon, if I recall correctly.  I've several S50s in my 
data center, hammer the fool out of them, and am happy.  Prior to them, 
we used Foundry EdgeIron1G switches for our gigabit-connected clusters. 
  They worked well.  For our newer gigabit-connected cluster we went 
with the HP 5412zl, and have been happy.

I'd not recommend cheap switches: They can bite you if you go too cheap 
and result in poor MPI and I/O performance.

gerry
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