SFF-8087 to fanout cable question

Michael Fuckner michael at fuckner.net
Sun Dec 14 08:33:55 PST 2008

> Like some of you who have built big ZFS arrays on multi-port controllers,
> I've got a mess of cables in my chassis... Now I have some SAS backplanes
> with mini-sas (SFF-8087) plugs. I know they work because I've used them
> with an Areca 1680 controller and some standard mini-sas cables. I decided
> that I wanted to go a different direction, and purchased an ASUS P5BV/SAS
> board that has a builtin 8-port LSI 1068-based SAS controller (and I
> highly recommend it). Now I have the 4x SAS to SFF-8087, and it doesn't
> want to work... But it worked going from the Areca controller to a regular
> 8-port SAS/SATA backplane.

> Are these cables only usable in one direction?


Multilane-multilane cables are all the same (even if some vendors have
different part numbers for different directions). If you connect discrete
ports to a multilane-backplane you need a reverse break-out cable.

See: http://3ware.com/products/pdf/3ware_Cable_Brochure.pdf

In contrast you need forward breakout for multilane controllers and
discrete backplanes.

> In summary:
> mini-sas (controller) to mini-sas (backplane) - works
> mini-sas (controller) to 8-port SAS/SATA (backplane) - works
> 8-port SAS (controller) to mini-sas (backplane) - nada
> 8-port SAS (controller) to 8-port SAS/SATA (backplane) - works
> Any ideas? Sorry if this is just a "duh" question. I don't do this for a
> living, I'm just obsessive about my media server :)
Trust me, it took me quite a while to figure this out...

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