2. Generally, you will need a special PCI card (usually 64-bit for the performance, but 32-bit cards are available) to use SCSI-drives.
The interface has different advantages than IDE / SATA as well... for example, at the moment, you can fit 15 SCSI drives on a single cable (16 IDs total, with the controller occupying one ID).
The SCSI RAID card I use is generally available for $10, has a battery backup built in, and can control up to 45 drives (3 "channels").
In general, SCSI drives are much more expensive than IDE / SATA drives. On the other hand, a quick E-bay search tends to find large companies liquidating thousands of large SCSI drives for dirt cheap (for example, I picked up 5 180G SCA SCSI drives for $100). Picking up drives this way tends to have other risks as well... for example, my last batch of drives obtained this way (10 18G) had a block size of 516 bytes... which meant that no PC-based OS could use the drives (wonder what it was used for?). Luckily, I knew enough to change the block size back to 512 bytes (firmware re-write) and use them, but it is buyer beware out there.
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Primary
CPU: Athlon 64 X2 4400+ Mobo: Biostar N4SLI-A9 RAM: 2G Crucial (DDR400) Video: eVGA GeForce 7900 GTX (512M) Audio: HDA X-Mystique HD(s): Maxtor 300G SATA2, Samsung 400G SATA2 OS(s): WinXP x64 Pro, Vista x32 Ultimate, Gentoo x64 Monitor(s): Primary - 19" Flat Panel (1280x1024) Secondary - 19" Flat Panel (1280x1024) Tertiary - Zenith 42" Plasma TV (1024x768 res)
Many other machines... sig too short