We're trying 2 disks per bus, 6 busses.  Hopefully, this won't 
exceed the cable length requirements.
-Brian
On Jan 17,  7:30am, Manuel Bouyer wrote:
} Subject: Re: Many PCI IDE cards in one box, is this possible?
} On Tue, Jan 16, 2001 at 10:10:23AM -0800, Brian Buhrow wrote:
} > 	Hello folks.  We're trying to build a fairly large RAID array of IDE
} > disks on a NetBSD 1.4.2 system using Promise Ultra DMA PCI IDE controllers.
} >  We've got 3 Promise cards with 4 drives each, for a total of 12 drives for
} > the array, plus the onboard Motherboard IDE for the boot disk.  The machine
} > seems to boot fine, but after a few minutes of operation, all activity
} > comes to a halt and everything seems to hang.  While this arrangement of
} > drives and cards seems reasonable, I have never tried to run 7 IDE busses
} > in one machine at the same time.  Are there limitations in the drivers,
} > that people are awareof, which could hamper our effort on this project?
} > Would 1.5 work better in this respect?  Does anyone have any experience
} > with trying to pack so many drives in one case?
} 
} I've actually got problems with 4 fast disks on channels: machine hang
} under heavy I/O (hard hang: no kernel messages, can't enter ddb -
} I suspect PCI lockup) The same machine was happy with 2 slower disks as master.
} Keeping only one disk per channel (at the expence of a promise Ultra/33 :)
} Solved the problem.
} 
} 7 IDE busses shouldn't be a problem, but 2 disks per channel migth.
} Also I can't see how you'll put 12 disks in a box; you may exeed the max cable
} length for UltraDMA.
} 
} --
} Manuel Bouyer <bouyer@antioche.eu.org>
} --
>-- End of excerpt from Manuel Bouyer