[cluster-l] Networking Equipment

[Jim Phillips]

On Wed, 28 Mar 2007, Nils Oberg wrote:

>
> I'm purchasing a 10-node cluster and the interconnect is going to be
> gigabit Ethernet.  The plan is to purchase a 24-port unmanaged
> switch.  I have a few questions regarding equipment quality:
>
> 1. Does the vendor matter, or are all 24-port unmanaged switches created equal?

If they have the same backplane bandwidth then they're probably the same 
performance, but I can't guarantee that.  We've used SMC switches, and 
while I noticed that the unmanaged switch we bought as a replacement is 
slower than the older managed switch, it doesn't affect the overall 
application performance.

> 2. Are there better networking cables than others?

The ones from ECE stores were pretty good.  You want something with the 
nice flexible guards on the end, rather than just crimped on.

> 3. All of the nodes I'm purchasing have two gigabit Ethernet
> ports.  Is there a way to bundle these ports together to get twice
> the bandwidth/half of the latency of a single port?

You'll never get lower latency.  The early Beowulf projects used channel 
bonding to double bandwidth, which needs a second switch and you can't 
boot over the network.  You could try giving each machine two addresses 
and plugging it into the switch twice, then setting up routing to use 
different ports for even and odd nodes.

With three 8-port switches you can do a flat network neighborhood 
(http://aggregate.org/FNN/) with up to 12 nodes.  I'd like to hear how 
that works if you decide to try it.

-Jim