Re: IDE-DMA strangeness (another one)

Mark Lord (
Tue, 01 Dec 1998 20:35:37 +0000

Rik van Riel wrote:
> Hi,
> I've just moved my IDE disks around, taking out an old
> disk and moving my new 6.4GB disk from hdd to hda.
> With this move I saw in improvement (hdparm -t) from 3
> to 8.4 (!) MB/second... Now I wonder what kind of bug
> in the Linux I/O subsystem could hold performance back

Heck, I see wild swings without moving anything around.

Sometimes my induhvidual drives show 13MB/sec,
sometimes they show 8MB/sec.

Sometimes my raid0 shows 22MB/sec, sometimes 18MB/sec,
and sometimes 6MB/sec.

Just weird scheduling effects or buffer-cachisms
on an otherwise idle machine. Most peculiar.

(author of hdparm)

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