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

Richard Fish (
Fri, 04 Dec 1998 11:47:40 -0700

Harvey Fishman wrote:
> In general, you will get less performance from a capable
> O/S using ATA interfaced devices than with SCSI. Of course, the ATA
> devices can cost a lot less, so it is a situation where you must determine
> how much performance you are willing to pay for.

I agree with you, but I'm gonna throw my $.02 in just to confuse things
some more... ;>

I recently got to test SCSI vs IDE drives in the same system. My tests
involved raw disk read (with hdparm), filesystem access (by making a
backup), and loaded filesystem access(by dd'ing from the raw drive to
/dev/null, while performing a filesystem backup). Both drives were
7200rpm, with UDMA enabled on the IDE drive. The SCSI drive was a 9GB
Quantum Atlas UW, which cost $370, and was attached to a Mylex BT950 UW
controller (~$250). The 6.5 GB Seagate Medalist PRO drive cost $225.

My tests had the following results (in K/sec):

Raw Read: 13358 9423
Filsystem: 5174 4780
Loaded: 478 1511

As you can see, the first 2 cases the IDE drive won, but severly lost on
the 3rd.

Now, before I get flamed, I will admit that it is certainly possible to
put together a SCSI system that beats IDE for all cases. With unlimited
funds, ANYTHING is possible... :>

And for the 3rd case, my test is probably not really indicative of a
real-world situation. But it does show that at some level of high IO,
multi-user, multi-process environments, SCSI will have a clear ad
It would be very interesting to repeat the above with 2 UDMA drives
using an md/raid0 configuration.

Richard Fish                      Enhanced Software Technologies, Inc.
Software Developer                4014 E Broadway Rd Suite 405                    Phoenix, AZ  85040 
(602) 470-1115          

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