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Promise (and most likely, other companies,) makes a port expander card. This is an older card, but still does the job. EIDE compatible, no UDMA on this one. This will give you 4 IDE channels (most modern motherboards have 2 built in, this gives you an ADDITIONAL 2 channels.) It can be found here. Note: This is an ISA card.

Promise also makes their Ultra33 expander card. This card supports UDMA33, and once again, adds an additional 2 channels. It can be found here. Note: This is a PCI card.

For those who really want speed, once again, Promise comes through with their Ultra66 expander card. This card supports UDMA66, and, like their previous cards, adds 2 channels, leaving your original 2 free for other devices (or more hard drives). It can be found here. Note: This is a PCI card.

By giving your machine 4 IDE channels, you will have the option of connecting up to 8 IDE devices, including hard drives, cd-rom drives, and the like. You should (if I'm thinking correctly..) be able to read/write from 4 of these devices simultaneously (one device from each channel). This is probably what the HOWTO or whatever is talking about (needing 3 controllers/channels/whatever). Accessing 2 devices on the same channel will be somewhat slower.

Personally I use a Promise Ultra33 controller and two 8.4 gig Western Digital drives under FreeBSD's vinum (striped) with great results. I picked up the controller for $26 at a computer show recently. Performance-wise, on a single controller (master/slave configuration), performance was about equal to a single drive. With each drive set up as the master on each of the Promise's controllers, I can get ~13 M/sec (dd-stone) continuously. I had to hack the driver a bit on FreeBSD, but Linux didn't seem to have a problem with it.

Thanks, but after a little ferretting, WD's site takes you here.