[Beowulf] The move to gigabit - technical questions

Jim Lux James.P.Lux at jpl.nasa.gov
Wed Mar 16 12:22:29 EST 2005


At 06:41 AM 3/16/2005, Robert G. Brown wrote:
>On Tue, 15 Mar 2005, Vincent Diepeveen wrote:
>
> > At 05:41 PM 3/14/2005 -0500, Glen Gardner wrote:
> > >Gigabit will be a little faster than 100Mbit on a small cluster, but not
> > >a lot.
> >
> > What is 'not a lot'.
> >
> > I would guess it's factor 10 faster in bandwidth?
>
>(Maybe, you don't get QUITE 100% of the raw clock advantage in all
>applications on all hardware, Vincent;-).  However, for most
>applications on most hardware you >>should<< get a signficant advantage
>-- 80-95% of 10x, or 8-9.5x.  Not a just "a little".
>

One might want to go back through the archives and see what the difference 
between 10 Mbps and 100 Mbps Ethernet was, and more to the point, why it 
wasn't 10x faster.  While the details might change, the basic issues remain:
"wire speed"
"protocol overhead"
"physical interface to PC's CPU"
"drivers"



James Lux, P.E.
Spacecraft Radio Frequency Subsystems Group
Flight Communications Systems Section
Jet Propulsion Laboratory, Mail Stop 161-213
4800 Oak Grove Drive
Pasadena CA 91109
tel: (818)354-2075
fax: (818)393-6875


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