Re: SSA cabling
From: John Jolet (john.jolet_at_FXFN.COM)
Date: Wed, 12 Nov 2003 18:07:34 -0600 To: aix-l@Princeton.EDU
when i set up a raid 10 on ssa last time, it would not let me span adapters with the raid, which i found odd at the time.
From: IBM AIX Discussion List [mailto:aix-l@Princeton.EDU]On Behalf Of
Sent: Wednesday, November 12, 2003 5:42 PM
Subject: Re: SSA cabling
If your adding a drawer and you have 2 adapters, and plan on having a raid
10, I would set up for redundant drawers with redundant ssa adapters so if
any single adapter or drawer fails you system will remain running in
Let's say you want to set up a raid 10 for 72gig and have 9 gig drives;
ssa0 a1 to drawer 1 slot 1
ssa1 a1 to drawer 2 slot 1
ssa0 a2 to drawer 1 slot 8
ssa1 a2 to drawer 2 slot 8
Identify your pdisks via diag and then create your raid 10 array setting the
pdisks in drawer 1 slots 1-8 as primary and drawer 2 slots 1 -8 as
Map it all out in a diagram and you will see your covered. The exception I
have found is if you have write cache then both ssa adapters talk to each
other to coordinate writes and if a write cache card fails you could be
screwed. Another key thing to keep in mind is all disks in an array must be
contained in 1 loop but you can have several arrays within a loop.
----- Original Message -----
From: "-ray" <ray@OPS.SELU.EDU>
Sent: Wednesday, November 12, 2003 3:59 PM
Subject: SSA cabling
> I'm setting up a new 7133 drawer and need some advice on cabling. Our
> current drawer is connected to two adapters. 2 RAID-0 stripes, and an AIX
> mirror. Is the correct cabling? It's been running in production like
> this for years:
> SSA1 7133 SSA2
> B2 4 |-- 1 B2
> B1 5 | 16--| B1
> | |
> A2 ---- 8 | 13 |--A2
> A1 -- 9 12 A1
> | |
> So on the 1st adapter, A2->8, A1->1, 2nd adapter A2->16, A1->9.
> For the new drawer, i'd like to do RAID-10 in hardware. It's also connect
> to two separate adapters. The first config i did looks like this and
> seems to work fine:
> 1st adapter A2->8, A1->9, 2nd adapter A2->1, A1->16.
> But the "Understanding SSA Subsystems" book seems to suggest this cabling
> for a "Simple loop with two adapters":
> 1st adapter A2->8, A1->9, 2nd adapter B2->1, B1>16.
> Any advice as to which is more correct?
> Ray DeJean http://www.r-a-y.org
> Systems Engineer Southeastern Louisiana University
> IBM Certified Specialist AIX Administration, AIX Support