Cisco MDS PortChannel over long distances, variation in cable length

[Cmorrall]

When designing a new SAN connecting two datacentres over some distance the question came up if we could use multiple dark fibres to create a PortChannel (ISL trunk in Brocade-talk I guess).
The restrictions on a Brocade equivalent came to mind; I can't have too much variation in the cable length in each individual cable in a trunk.
However, I've been unable to find much if there are any such restrictions for Cisco MDS. I found something a bit vague in a marketing flyer for Cisco MDS where they pointed out that a "competing vendor" [duh] has this restriction whereas Cisco does not.

Poring through the manuals, so far no mention of this. I suppose if there weren't any restriction, it wouldn't be mentioned.

Any comments?

[andrewB_1]

Charles - did you get anywhere with this?
Am planning to set this up with my existing MDS9134's

HP, Cisco and EMC have assured me the configuration is supported but I can't find anyone who has actually set this up and can verify that its more than "airware".

Any feedback on your experience so for would be very welcome.

[Cmorrall]

I used two physical pairs of dark fibre, but I also installed a CWDM solution to split these two pairs into four connections. I connected each switch to both physical fibres, but logicially seperated on different wavelengths. Might sound confusing if you're unfamiliar with CWDM.

The net result was that I had two fabrics with two ISLs in each fabric, and they take two different paths per fabric. So far, I can get link OK, but I've not put any load on the connections yet.