[ale] nfs & collisions

[hbbs at attbi.com]

Correct me if I'm wrong, someone, but in an Ethernet hub, I don't think there 
is an *electrical* commonality between the ports the way there would be if you 
were srtinging thickwire or thinwire.  This means that there has got to be some 
meaningful delay between activity at one port and any other in a hub.  Put two 
hubs together and Hub B can't even begin to react to traffic on a port on Hub A 
until the port on Hub A to which Hub B is connected reacts to traffic elsewhere 
on Hub A.  Ordinarily this latency is not a big deal, but if you are trying to 
push big stuff around, then it is, and I get the feeling that the time spent 
detecting and resolving collisions goes up too, because it takes longer for the 
collision *and* its resolution to propagate.

Remember, an Ethernet collision is basically an "excuse me; try again."  The 
overall effect of adding latency to that process is not unlike watching Bill 
O'Reilly argue with someone via satellite.

- Jeff
> On Mon, Feb 24, 2003 at 05:10:53PM +0000, hbbs at attbi.com wrote:
> > If you're trying to push ~20GB between two machines through four unswitched 
> > (and I presume 10base-T) hubs, then, yeah, it's gonna collide like a SOB and 
> > take 31 hours.  At the very least, get the two machines on the same hub, but, 
> > better yet, put a 10/100 switch in place.  Just because the four cascaded hubs 
> > works doesn't mean it works efficiently.  The latency is just going to be 
> awful.
> 
> <tangent>
> Would putting the two machines on the same hub really make any
> difference?  I thought unswitched hubs always broadcast all traffic over
> all ports.  Or is an unswitched hub still smart enough to broadcast the
> traffic only on the local ports if the destination address is local?
> Just curious.
> </tangent>
> 
> Jason
> -- 
> Jason Day                                       jasonday at
> http://jasonday.home.att.net                    worldnet dot att dot net
>  
> "Of course I'm paranoid, everyone is trying to kill me."
>     -- Weyoun-6, Star Trek: Deep Space 9
> _______________________________________________
> Ale mailing list
> Ale at ale.org
> http://www.ale.org/mailman/listinfo/ale
_______________________________________________
Ale mailing list
Ale at ale.org
http://www.ale.org/mailman/listinfo/ale