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Subject: Re: SCSI, U2W in particular?, and poor performance...
From: Dylan Griffiths (Dylan_Gbigfoot.com)
Date: Sun Mar 05 2000 - 14:08:54 CST

Sander Steffann wrote:
> Why is everybody doing so difficult about this instead of trying to help?
> The guy mentioned that he replaced the SCSI disk in the fast machine with an
> IDE disk, and is still noticing a difference in favor of the IDE disk. This
> means that on the same installation/configuration, with the only difference
> the SCSI/IDE disk, there is a difference. He only asked if anybody had an
> idea what could cause this.

It could be a problem with the Linux SCSI subsystem. While stable, is it
somewhat evil code as of the 2.2.x kernel revisions. Much works has been
done in the 2.3.x development series to clean up the SCSI subsystem (with
good results). Also, the SCSI HDs likely support TCQ (tagged command
queing), but this is not enabled by default in the Linux kernel for
compatibility. I suggest he tunes the Linux kernel SCSI AIC7xxx driver
parameters before he does anything else, as the "most compatible" SCSI mode
is slower than the "best speed" mode of IDE (which is also default).

Otherwise, this is not a postfix issue, nor does it nessitate further
discussion/flaming on this list. 

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