Re: Dumb question: Which is "better" SCSI or IDE disks?

Kurt Garloff (
Fri, 4 Dec 1998 10:05:11 +0100

On Thu, Dec 03, 1998 at 12:12:03PM -0500, Russell Leighton wrote:
> What are good rules of "thumb" for
> choosing IDE vs SCSI when building
> a Linux system?

(1) Price ++ -
(2) Speed + ++
(3) Speed when accessing more
than one disk at a time - +
(4) Extendability 4 7/15
(5) Reliability o +

For a home machine, I'd choose IDE, because of the price.
If you want your SCSI disks to be faster (single disk access), you need to
buy 7200rpm disks, which is probably not what you want at home (noise,
If you plan to put multiple disks (and maybe CD-Rom, ZIP, Scanner ...), than
you might consider SCSI. SCSI disks disconnect form the bus after they
received a command and reconnect to transmit the data later, which allows
for good sharing of the bus between multiple disks. IDE does not allow other
disks to transfer data, when one is busy.
With DMA2/UDMA the high CPU load for transfering Data to/from IDE disks is
no longer there. With UDMA, there is also some error checking for the
transmission. (SCSI does this since many years.)
Note that SCSI cables can be 3m (1.5m with Ultra SCSI) long, while IDE only
45cm. So if you you want to have a big tower, you IDE disks must be placed
near the mainboard ...

So, IMHO, SCSI is the much better design, but you only profit in some cases
as DMA2/UDMA has solved the CPU load problem for IDE. You have to check
whether the SCSI advantages are worth the price for your application.

Just my E0.02 ...

Kurt Garloff <>  (Dortmund, FRG)
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