[rescue] FDDI in the real world babble

[George Adkins]

> > to a ring. And you can mix DAS and SAS cabling.
>
> So, quick question then.  I have a cresendo card that is SAS.  I have
> a Lanplex 2500 that is DAS (I also have a concentrator that is SAS,
> but I'm hoping to ignore it for the first step).  What do I need to do
> to hook the two together?  Just buy a SAS cable, and find a software
> setting on the lanplex?  Find an adapter cable?  What?

Any DAS interface will function as a SAS interface through the "A" port, of 
if there is no ring detected on the "A" port, it will fail over to the "B" 
port.  So, the short answer is, Yes, you can use one of the ports on a DAS as 
a SAS.

<longer explanation for those interested>

In fact, you could, for instance use this feature for redundancy.  Let's say 
you have two complete dual attach FDDI rings (redundant) and at points along 
those rings, you put pairs of concentrators with single-attach ports, one on 
each ring.

Now, you attach Dual-Attach stations to those single attach concentrators, 
with a single-attach line running from the primary ring's concentrator to the 
"A" port, and the secondary ring to the "B" port.

Now, if the concentrator fails, the DAS card will switch over to the 
secondary ring ("B" port) automatically, eliminating any single point of 
failure upstream from the NIC.  
If you put in two NIC's (Dual Dual attach) you can have failover at that 
level as well, removing all single points of failure

George