The advantage of SCSI is that it is very fast. However, the drives and controler cards are expensive compared to the typical desktop hard drive. Also, the storage capacities are on the smallish side. If you are going to get SCSI be prepared for a high pitched whine which comes from the 10,000 to 15,000 rpm speeds that the drives run at. Also, don't think about running it without some type of hard drive cooler. For the typical desktop user SCSI is not recommended. SCSI drives are optimized for server environments where they dish out small files very quickly. For desktop users, I would recommend a regular ATA hard drive with a large cache, such as 8mb. Maybe get two and put them in RAID 0 for performance. However, if you plan on running a server, SCSI can be invaluable.

I would agree - basically, the 'extra performance' of SCSI is not worth the extra cost for a desktop. And ATA drives have come on leaps and bounds in recent years - they are much closer in performance to SCSI drives than they were eg 10 years ago. In fact, I have a feeling that for *desktop* usage the top ATA drives are actually faster than their SCSI counterparts. Have a look at http://www.storagereview.com for reviews, performance comparisons, etc.

SCSI (Small Computer Systems Interface) was designed initially to be a jack-of-all-trades kind of interface. I may repeat some of what has already been said for the sake of making my answer as complete as I can. Advantages: 1. SCSI can handle a wide variety of devices: hard drives, scanners, plotters, CD drives, and the list goes on. 2. A SCSI controller can communicate with up to 7 or 15 devices depending on the version. I am sure work is being done to add more. 3. It is often easier to install and setup a SCSI device than with many other device interfaces. (This comment is not limited to the SCSI vs. IDE issue. See Advantage #1 for the scope of what I mean by "device." I also say it is "often easier," not "universally easier.") 4. SCSI controllers and devices are intelligent, they have microcontrollers, if not full blown processors, inside them. They do not require software-base contoller drivers like some Windows devices, putting less load on the CPU. 5. SCSI has proven itself to be a good platform for moving and storing large amounts of data. Recent developments with SCSI have focused on exploiting this feature even further. 6. Newer SCSI devices and controllers are supposed to be backward compatible with older SCSI devices and contollers. (from my own personal experience, this is about 95% true) 7. Recent SCSI contoller and devices currently offer the highest through-put for any peripheral connection scheme currently available. 8. SCSI drives are, on the whole, more reliable than ATA/IDE drives. Disadavntages: 1. SCSI has never been cheap. 2. There are at least a dozen different versions of SCSI: narrow, wide, fast, ultra, SCSI-2, ultra-wide, Ultra 320, fibre-channel and more. 3. There are 3 different port interfaces for connecting internal SCSI devices: 50-pin, 68-pin, and 80-pin. You can buy adapters to convert from one kind of connector to another. 4. There are even more port interfaces for connecting external devices. I know of at least 4. You can buy cables that convert from one port interface to another. 5. SCSI drives generally run at higher RPMs than ATA/IDE drives which creates more heat and noise than their lower RPM counterparts. 6. When something breaks, SCSI drives are more difficult to repair than ATA/IDE drives. (or so I was told by a colleague who used to do physical repairs on hard drives)