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It's true that EIDE drives have seek times as high as those of SCSI drives. But
seek time does not tell the whole story. Up until 2001, SCSI had a much faster data transfer rate than
IDE. Now, even that has been turned around--IEDE drives have faster data
transfer rates than do the traditional SCSI drives. You can buy a very expensive
latest-generation SCSI that will beat a modern EIDE drive, but that gets into
extreme cost for marginally useful performance. SCSI still has one advantage over IDE of any flavor: it doesn't bog down your CPU to do its job. IDE, in fact, uses nine times the
resources SCSI does for the same operation. With Pentium-III and faster
processors, this overhead is usually inconsequential. At one time, the argument
against IDE was that any average
horse could have beaten Secretariat--if Secretariat had to carry 9 jockeys and the other
horse had to carry only one. This metaphor illustrated that no matter how fast
an IDE drive became, its resource requirements would bog down the whole
system. But, this metaphor is no longer true when it comes to CPUs because
a modern CPU in an IDE system isn't carrying nine extra jockeys. It is carrying
nine extra ounces on a jockey--something that may not make a noticeable
difference at all.
A big advantage of SCSI is you use only one IRQ (Interrupt ReQuest)
to drive up to 10 devices. This has system expansion implications that are
rapidly becoming inconsequential. Let's see why.
We pronounce IRQ "Eye-Are-Que," (Hey, so am I!), but
I think we should pronounce it "Irk." It really irks me that you need an IRQ for
each IDE device. At one time, if you added anything to your system, you'd start having IRQ conflicts.
You can run out of IRQs, and that means devices compete for processor
attention--often crashing the system as they do. This made a strong case for
SCSI. In a two HDD (hard drive) system with a
CD-ROM and scanner, you can free up 3 IRQs simply by going to SCSI. That leaves more for
your video card, sound card, modem, and mouse to fight over. You have only 15, and most of
those are reserved.
But, a way around this conundrum is to use USB peripherals
and devices. A USB scanner, backup drive, mouse, CD-burner, printer, etc., and
you suddenly free up IRQs. Another way around this conundrum is to abandon the
single desktop model completely. Computers are so cheap these days, you can
build (or buy) two IDE-based systems and network them together for less money
than you'd spend on a comparable SCSI-based system. The advantages of this are
immense. For example, you can back up the files of each system to the hard
drive(s) of the other. You can also have one machine set aside for CPU-intensive
tasks like CD-burning or whatever, while the other machine is 100% available for
use. If you have a system failure in one machine (e.g., Windows needs complete
reinstallation or your CPU croaks), you can still work.
Just a few years ago, SCSI was the clear champion. Today,
that isn't so. If you have the older SCSI systems, it is especially not so. The
IDE loading problem on a system is not a concern if your processor is at least a
Pentium-III-500 , and USB resolves the IRQ issue. Plus, networking two IDE
machines--perhaps an older one and a new one--will leave any SCSI "Swiss
Army knife" computer in the dust. You have more than twice the available
CPU power and many, many other advantages that simply make the SCSI advantages
irrelevant.
So, don't spend big money on a SCSI system for your
desktop. If you are in the server and RAID array world, or have high-end needs,
you may want to spring for a high-end SCSI system. But for even power users,
today's IDE runs circles around yesterday's SCSI. Especially if you spend the
same money creating a peer-to-peer network of two machines.
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