Best way to cable 3 SSA drawers to 2 systems with 2 cards each? 1

[bi]

Does anyone have any advice and/or examples of cabling 3 full drawers of SSA disks to 2 systems, each of which have 2 SSA cards?

I would like both systems to be able to see (but not necessarily use) all of the disks. And I would like each system to have two paths to each of the disks. Is that possible?

 

[bimux]

Well, You are in luck ... You can do almost anything with SSA. But you have to be carefull if you have the FastWrite Cache (you are limited to max 2 adapter per loop). You have to decide if you need availability in case one of the adapter fails. Pay atention to auto-bypass J1-J16 J4-J5 J8-J9 J12-J13. You also have to consider the RAID options (miroring, RAid5 or 10 ).
You shouldn't mix A and B channels.
Are both servers in production ? ... if not you have to be sure that if the second one goes ofline you do not lose paths.

Here is a simple layout.
Server1_SSA1_A1 to Tower1_J1 ....
.... Tower1_J8 to Server2_SSA1_A1 ....
.... Server2_SSA1_A2 to Tower1_J9 ....
.... Tower1_J16 to Server1_SSA1_A2 loop completed.

Server1_SSA2_A1 to Tower2_J1 ....
.... Tower2_J8 to Server2_SSA2_A1 ....
.... Server2_SSA2_A2 to Tower2_J9 ....
.... Tower2_J16 to Server1_SSA2_A2 loop completed.

Server1_SSA1_B1 to Tower3_J1 ....
.... Tower3_J8 to Server2_SSA1_B1 ....
.... Server2_SSA1_B2 to Tower3_J9 ....
.... Tower3_J16 to Server1_SSA1_B2 loop completed.

Here is another way to see it and to gain some performance and redundancy.
Server1_SSA1_A1 to Tower1_J1 ....
.... Tower1_J8 to Server2_SSA1_A1 ....
.... Server2_SSA1_A2 to Tower1_J9 ....
.... Tower1_J16 to Tower2_J8 ....
.... Tower2_J1 to Server1_SSA2_A1 ....
.... Server1_SSA2_A2 to Tower2_J16 ....
.... Tower2_J16 to Server2_SSA2_A1 ....
.... Server2_SSA2_A2 to Server1_SSA1_A2 loop completed.

Server1_SSA1_B1 to Tower3_J1 ....
.... Tower3_J8 to Server2_SSA1_B1 ....
.... Server2_SSA1_B2 to Server2_SSA2_B1 ....
.... Server2_SSA2_B2 to Tower3_J9 ....
.... Tower9_J16 to Server1_SSA2_B2 ....
.... Server1_SSA2_B1 to Server1_SSA1_B2 loop completed.

Now bare with me ... the next one is a bit more complicated but gives a performance boost if you have a lot of activity to HD. Be carefull because with this one you depend on the 2th server if you loose a SSA adapter on the 1st server.

Server1_SSA1_A1 to Tower1_J1 ....
.... Tower1_J8 to Server2_SSA1_A1 ....
.... Server2_SSA1_A2 to Tower2_J8 ....
.... Tower2_J1 to Server1_SSA2_A1 ....
.... Server1_SSA2_A2 to Tower3_J1 ....
.... Tower3_J8 to Server2_SSA2_A1 ....
.... Server2_SSA2_A2 to Server1_SSA1_A2 loop completed.

Server1_SSA1_B1 to Tower1_J16 ....
.... Tower1_J9 to Server2_SSA1_B1 ....
.... Server2_SSA1_B2 to Tower2_J9 ....
.... Tower2_J16 to Server1_SSA2_B1 ....
.... Server1_SSA2_B2 to Tower3_J16 ....
.... Tower3_J9 to Server2_SSA2_B1 ....
.... Server2_SSA2_B2 to Server1_SSA1_B2 loop completed.

Have fun !
)

 

[bi]

Thanks, bimux. I'm going to take this home and draw it out. I'm sure one of these configurations will be perfect.

 

[ulah]

Hello BI

For a really great tutorial on SSA go to the link below, which is the IBM Red Books home page and down load .pdf or view on line .html

70. Understanding SSA Subsystems in Your Environment
Published on April-30-2000

http://publibb.boulder.ibm.com/Redbooks.nsf/Portals/UNIXRedbooks

This IBM Red Book is the best-documented tutorial that is available for the IBM SSA architecture. And best of all it is free.

Regards Ulah