On 10/11/12 10:05, Adam Levin wrote:
Here's the problem: when we run cables from HBAs (in hosts or in
storage systems) direct to the switches, the Tx and Rx are correct.
When the lightguide patch is in the middle, the Tx and Rx are reversed.
Some time ago, almost ten years now, when we started hooking things up
in a newly-renovated server room, it took a while to figure out which
part of the storage path was borken. Turned out that the connections
between patch panels was straight-through.
What I'm not sure about is what is normal for this configuration? Do
people normally buy "crossover" FC cables to use with a patch panel,
or do people buy proper patch panels which "uncross" the streams?
In my opinion, all duplex fiber should be crossover, even the runs in
walls between patch panels. That way you have a net twist, everything
has Rx connected to Tx. (You will run into a problem if you use any
passive bulkheads (FDDI had some, SC could too))
If the panels are straight, then the conections can be kludged in one
place (of four possibilities, since these were SC-LC cables) by
unclipping either end (and not reclipping to make a straight cable),
making the problem a little more noticeable. Alas I wasn't in charge
of that room and nobody ever fixed the parity on the panels, as far as I
know...
--
Jeff Woolsey {woolsey,jlw}@{jlw,jxh}.com [email protected]
Spum bad keming.
Nature abhors a straight antenna, a clean lens, and unused storage capacity.
"Delete! Delete! OK!" -Dr. Bronner on disk space management
"Card sorting, Joel." -me, re Solitaire
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