This same tantalizing idea has intrigued me on and
off for years: a PeeCee with some cheap IDE drives
and a SCSI controller in it is theoretically all you
need to make a RAID box. Unfortunately, there I've
always been too busy with other things to get beyond
the "Wouldn't that be cool!" stage.
Two problems that come immediately to mind are
(A) getting your HBA+OS to act in the role of SCSI
target, and (B) performance. A generic Linux-style
solution to A will almost certainly degrade B, while
a customized solution to A probably means you don't
get to leverage as much existing code as you'd like.
Solving B means obsessing about latencies/throughput;
doing all the RAID striping/mirroring junk while
absolutely minimizing the amount of time you spend
servicing interrupts, copying data, context switching, etc...
>Can SCSI controllers talk to SCSI devices attached
>to DIFFERENT SCSI controllers?
I'm not sure I understand your question but if you're
asking whether multiple HBAs can be on the same cable,
then Yes, because SCSI devices aren't "attached"
to SCSI controllers - SCSI devices are all peers,
just like Enet devices. Using old-style SCSI (with
its 8 possible device IDs) as an example there's
nothing (technically) to prevent you from having the
HBAs from seven different computers all connected
to the same SCSI cable and talking to one single
(desperately overworked) disk.
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