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Serial ATA vs. SCSI - Will it Compete?
fazzumar asks: "I've been checking out serial ATA (SATA) and it seems like it's got a lot of potential. The first generation spec was finalized August 2001 and members of the SATA group anticipate a 12-18 month acceptance period. They've planned for a cut-over phase and adapters that allow connecting SATA devices to ATA adapters and vice versa. The cables alone are a worthwhile advantage (4 pins, up to 1 meter in length), and the 150MB/sec bandwidth is a (minor) improvement over current ATA drives & adapters. Infoworld has a story on SATA that provides a few tidbits of information. What I really want to know is, will manufacturers of the new host adapters be able to integrate many of the advantages that SCSI provides or will the cost of adding these features push the retail cost too high for the anticipated market?" I just picked up a new WD Hard drive just yesterday for the planned MP3 jukebox I hope to be building near the end of the summer. I really wanted to go SCSI, but couldn't. While the poster claims a near ~7x in price difference, I saw about a ~5x difference in my local store. Is SCSI in danger of falling behind IDE drives (especially serial IDE drives) in popularity?
"I love SCSI, and I can bring myself to accept the additional cost of the controller, but with IDE hard drive prices dropping, I frequently wonder if SCSI drive prices are artificially inflated. Just a few years ago, SCSI drives were ~10-20% more than IDE and now they're ~7X more than an IDE drive. (Seagate 10k RPM SCSI - ~18 gig for ~175. Western Digital 7200 RPM IDE - ~120 gig for ~175) If the option comes out to get SCSI performance from an IDE drive I'm going to take it."
Quote: The ATA drive subsystem has a high-bandwidth I/O bus that minimizes bottlenecks, even when all four drives are engaged at once. That's how Xserve can achieve a theoretical peak performance of up to 266 megabytes per second, compared to a 160MB/s theoretical performance with SCSI Ultra160 disk drives -- at a significantly lower cost, and while generating less heat than SCSI drives.
Hard drives prices are set by a complicated formula where somebody sits down, looks at the costs involved in developing the drive, the costs involved in testing the drive, the costs involved with creating the equipment to manufacturer the drive, the number of units they expect to sell, the expected return rate and the cost per unit of manufacture (and a lot of other things). They then attempt to set a price which will result in a reasonable profit.
Why attempt to set a price which results in reasonable profit? Because if one aims for an unreasonable per-unit profit, a competitor (and the hard-drive market is hardly a monopoly) will decide that they can sell enough extra units by lowering their price that they'll undercut the first vendor.
So SCSI drives happen to be the most expensive in nearly every fashion. They're the most likely to implement cutting edge technologies, thereby funding the refinement of these technologies for later use in cheap IDE drives. 15K RPM SCSI drives have been around for quite some time now, but I'm not aware of any IDE drives that beat 10K RPM yet.
SCSI sells fewer units, thus the fixed costs are distributed over a much, much smaller number of units, driving up the price dramatically.
SCSI drives are more likely to be returned as defective. Not because of a higher failure rate, but because SCSI drives are likely to be put places where they get used heavily, 24 hours a day. IDE drives tend to get used in applications which involve idling 98% of the time, so even cheap shit will have low return rates.
Additionally, the SCSI command set is larger than the ATAPI command set. In fact, ATAPI is just a standard way to communicate a subset of SCSI over an IDE connection. This means that SCSI drives really can do more things than an IDE drive... for instance, they can accept multiple commands, then execute them in a more intelligent manner than an IDE drive, which only knows how to do one thing at a time (IBM DTLA and DPTA not withstanding)... So this SCSI drive is also more complicated than the IDE counterpart, thus requiring more testing, and more design, raising the costs further.
Saying that SCSI is artificially overpriced is like claiming a WRC rally car is artificially overpriced, because you managed to get 500hp out of your Dodge Neon by bolting on a turbo, intercooler, straight pipes and a cold air intake.
Somehow I think that my explanation for the price disparity between IDE and SCSI is a lot more plausible than one which requires every single hard-drive manufacturer on the planet to be organized in a cabal, whose sole purpose is to drive up the price of server-class hardware.