[Beowulf] Slection from processor choices; Requesting Giudence

[J. Andrew Rogers]

On Jun 16, 2006, at 3:00 PM, Vincent Diepeveen wrote:
> Jeff, we know how some people can mess up installs, but if you have  
> gigabit ethernet,
> with a one way pingpong latency of like 50-100 us if you're lucky,  
> which is not using DMA i
> guess by default; in short nonstop interrupting your cpu, versus  
> newer myri cards that are probably under 3 us, factor 20 to 30  
> advantage to myri then you need to really not manage to install the  
> network to let gigabit ethernet work better.


I get a round-trip latency between Linux servers (vanilla CentOS  
install) across a metro GigE IP network of ~140 us, which I guess  
means we are "lucky".  I would hope that a dedicated, tuned, and very  
local GigE network could do a lot better than what I get between  
Internet servers separated by kilometers of fiber and various bits of  
network gear.  And I know it can.

You exaggerate the limitations of GigE.  Current incarnations of GigE  
can be close enough to Myrinet that it is perfectly functional for  
some applications and pretty competitive for someone willing to  
extract the capability from it.


J. Andrew Rogers (who admittedly has an above average IP network)