[DRBD-user] DRBD vs Linksys?

Jeff Buck jeffb at umci.com
Mon Aug 1 22:03:03 CEST 2005

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.

How long is the cable that you're using? I think there is an actual
required length with ethernet. I would try using a cable that is at
least six feet long when you're using a crossover if you're having
problems.  It seems unintuitive that too short a cable could be your
problem, because we all think short cable == strong signal... which is
actually true, but with too short a cable, the timings for sending and
receiving, and collision detection can get all screwed up. This is
actually the problem with too long a cable too. It's not that the signal
isn't strong enough after 300 feet of ethernet cable, it's that in the
time it takes the packet to go down the wire collision detection from
one end of the wire might not match the other end.. The same issues
could be true in reverse for too short a wire. The cards might think
everything seems like it's colliding because they're too close together.

I'm not an expert at all, and my guess/example could be way off base,
but I have definitely had cards wig out with a crossover cable that was
only 12 inches long. Two feet, they still wigged out. Eight feet, and
they were fine. That said, almost all of the cards we've used are just
fine with a 1 foot long crossover cable. Right now, that's what our main
fileservers use...


On Fri, 2005-07-29 at 22:14 -0400, Paul Bennett wrote:
> Are there any specific known issues with DRBD and Linksys "Instant  
> Gigabit" network cards? I may have found something in the realms of a  
> compatability issue with certain machines doing DRBD over a crossover  
> cable on these cards.
> I'm still investigating it. More details when I know them. I think it's  
> the fault of the card rather than DRBD, FWIW.
> Paul
> _______________________________________________
> drbd-user mailing list
> drbd-user at lists.linbit.com
> http://lists.linbit.com/mailman/listinfo/drbd-user

More information about the drbd-user mailing list