Re: Poor SCSI drive performance on SMP machine, 2.2.16

paradox3 (
Sun, 28 Jan 2001 17:57:47 -0500

> It sounds to me like you have a SCSI bus problem. Have you checked
> termination? Cable quality? Cable lengths?

Forgive me, I'm rather ignorant of SCSI hardware.....All that I have is a
cable (appears
to be good quality, came with motherboard) about 60 centimeters long going
from the
motherboard to my hard drive. There is an unused/empty port in between.

> Do you have tagged queuing enabled for aic7xxx? It's a config option
> and you can adjust the maximum queue depth. You can see the current
> settings by cat /proc/scsi/aic7xxx/0
/proc/scsi only contains a single file named "scsi" with brief info about
the drive
According to my last save kernel config, tagged command queueing is not
enabled by default.
Could this be the problem?

> Do you have write caching enabled on the drive? scsiinfo -c /dev/sdx
> will tell you if you do.
I don't seem to have scsiinfo.

> As a data point, I copied a 650MB file to another file on the same
> 10krpm disk and sync'ed in about the same time it takes you to write
> 100MB. I've also copied it from a slower 7200rpm disk to my 10krpm IBM
> drive and sync'ed in 1 min 19 secs which is about the read speed of
> the slower disk.
> --
> Trevor Hemsley, Brighton, UK.

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