increasing high load

Ulrich Hochholdinger hochhold at
Thu Mar 20 15:58:00 CST 2003

Setup is a PE 2650 / 2x Xeon 2.4GHz / 2 GB RAM with a Perc3/Di controller 
with  3x73GB HD configured as RAID5 (factory configured from Dell).

When I start writing a large file to disk
(dd if=/dev/zero of=bigfile bs=1024 count=8000000)
the system load starts to increase very high (to about 15) while writing 
this file, and the system becomes nearly unuseable. This also happens 
if someone makes larger read-disk access.
But top/ps shows CPU's are about 85% idle, and there are no processes
consuming really much cpu-time.

Filesystem is ext3. It also happens on ext2 Filesystems.

OS is Debian linux with Debian Kernel 2.4.20 / with highmem / highio
/SMP support and hyperthreading enabled.

afacli shows that there are no problems on the raid-controller.

Has anyone experienced similar behaviours? Or any hint where to search?
Google and this list-archive shows no answer for this problem.
Could this be a memory / hyperthreading / aacraid / or whatever problem.
Or do I have to change some settings on the raid-controller

I tested this with the same kernel on a (non-Dell) SMP-Box 
(Dual PIII 500 / 1GB RAM / normal AIC7X SCSI-Controller / software Raid), 
without any problems.


\ Ulli Hochholdinger                               E-Mail: hochhold at \
/ ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ /
\ Sometimes I think the surest sign that intelligent life exists elsewhere \
/ in the universe is that none of it has tried to contact us. (Calvin)     /

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