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SubjectRe: SMP 2.1.131: SCSI performance extremely poor vs. IDE

On 08 Dec 1998 16:31:07 -0800, Ben Gertzfield <> said:

> I've received a report of extremely poor SCSI performance in the late
> 2.1.x kernels and verified this under 2.1.131.

> I tested this by untarring the mozilla source onto the local hard
> drive, syncing, and rm -rf ing it.

> The mozilla source is 91.6 megabytes untarred.

> The results are astounding:

This "benchmark" is so full of variables that it is utterly meaningless
on its own. You are running on two different systems. Is performance
repeatable or not? How much memory is in each system? How fragmented
are the existing disks? How much of the data is in the buffer cache
when you do the rm?

> This is, frankly, terrible. Since when is IDE three times faster than
> ultra-wide SCSI?

IDE command setup latency is a _lot_ lower than SCSI's, especially with
UDMA. If all you are measuring is random read seek rates, then yes, IDE
can quite easily be faster than SCSI.


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