DIY shared SAS storage

Redundant controller means there are two of them. Easy? No! because next you need a backplane that supports double wiring to the disks and your case doesn't. Anyway, if you can fix that: what OS will you use for the box?

Re: double wiring - Now that you mention it, that may be another hurdle. Could I put a little SAS switch in there? On paper it seems possible...

Re: OS - depends on the controller's requirements. Dell's and Sans Digital's use only the firmware on the controller itself as the "OS" which is really to say the firmware has a standard web interface via ethernet.

/sigh

what are you trying to use it for, do you really need sas class storage?

'what are you trying to use it for' might be the right question. On top you said 'shared storage' and something about two cluster nodes. At least the MD3200 is a direct attached storage. The redundant SAS-controllers are part of the servers and the MD3200 provides basically external disks. I don't see how you want to share this? If you want to share the disks you need to go for an IP-storage (NAS). That's what the case you mentioned is mad for. There is space for a MB plus SAS-controllers for the internal wiring plus ethernet controllers for the external wiring. With the right OS this will provide the server nodes with either dedicated iSCSI-Space and/or shared file system. Example: NX3300

iSCSI is out of the question for several reasons. I don't have space to go over them here.

External raid subsystems that are capable of being used in either an Active-Active situation, or active-failover.

If you look at the MD3200 or 3220, they are both able to "present" virtual disks to any host servers available on the other side of the Host Bus Adapter.

Logically it looks like this:
Host Servers
vvvvvvvvvvvvv
HBA
vvvvvvvvvvvvv
SAS switch
vvvvvvvvvvvvv
SAS RAID Subsystem (MD3200, etc)

Sorry, but you lost me. I'm out.

Have you had a look at http://blog.backblaze.com/2009/09/01/petabytes-on-a-bud....
It's SATA not SAS - but designed to fit 67TB into a 4U rack mount space - has the instructions and parts list you need to build it.

Yeah I've seen that. My design isn't really similar to that. A build like that only has use as an Archive NAS.

What you did remind me, however, is that hardware raids may be a thing of the past with Windows Server 2012 Storage Groups. I know the guys at RAIDINC.com can enlighten me on build ideas...

I Think the controller used in Sans Digatal's solution might be Areca's ARC-8068, but unfortunately it seems there is no place to purchase it. Have to ask directly from Areca support.