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EMA 12000 G80 Multibus Cabling

Nicholas Sinish
Occasional Contributor

EMA 12000 G80 Multibus Cabling

We know that the standard multibus configuration for dual path is to cross connect the G80 Controller Ports:
A = Top
B = Bottom
P1 = Port 1 (left)
P2 = Port 2 (right)

In other words the standard config is that A1 and B2 be connected to Switch D1 and therefore one HBA Server Path, and then A2 and B1 be connected to the other Switch D2 and HBA Server Path.

We recently noticed that one EMA(3) is cabled correctly but the other EMA(5) is cabled the following way:

EMA3 Cable Layout:
A1 and B1 are connected to Switch D1 therefore HBA1 in each Server, and A2 and B2 are connected to Switch D2 therefore HBA2 in each Server. In other words they are not cross connected yet both Controllers are still connected per Path.

Can this cause Disk Corruption and/or problems with bringing Cluster Disk Resources Online?

What is the net effect of cabling G80's this way?


Mike Naime
Honored Contributor

Re: EMA 12000 G80 Multibus Cabling

It doesn't really matter, except that I think it is simpler to track the second way.

I have 36 HSG's cabled the second way. (12 RA, 24 EMA) I have VMS, AIX, and W2K on the same SAN. You get basically the same effect either way. The second way, I know that when looking at a mult-pathed LUN on a VMS system, paths ending in xxx1 and xxx3 are my RED fabric, and paths ending in xxx2 and xxx4 are the BLUE fabric.

What you are really tring to do is to ensure that you have 1 port connected to the RED and one port connected to the BLUE san fabric on both the TOP and BOTTOM controllers.

The key is to stay consistent across all of your storage controllers.

So to summarize for my setup, ports A1 and B1 are the RED fabric. Ports A2 and B2 are the BLUE fabric. I know that:
1 = RED Fabric.
2 = BLUE Fabric.
VMS SAN mechanic