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Date:      Thu, 24 Jul 1997 16:59:34 -0700 (PDT)
From:      Jaye Mathisen  <mrcpu@cdsnet.net>
To:        hackers@freebsd.org, scsi@freebsd.org
Subject:   Ugh, DPT killing my performance... :(
Message-ID:  <Pine.NEB.3.95.970724164859.19992Q-100000@mail.cdsnet.net>

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P6-200, 64MB RAM, DPT 2 channel Ultra Wide, plugged in to Seagate
Barracuda's.  (4GB).  DPT has 64MB RAM, version 1.10 DPT patch,
2.2.2-RELEASE disk.  All disks are on the same channel (0) of the DPT.

The following script renders the system essentially unusable:

while (1)

  (cd t1 && iozone 600)
  (cd t2 && iozone 600)
  bonnie -s 200 &

  wait
end


ls -l of /root takes > 20 seconds.  

TOP is showing > 99% idle time.

systat 2 only shows 28 interrups/sec on IRQ 15, which is the DPT
controller, according to the BIOS.  Transfers shows about 20-30 tps.


There are these occasional burps of > 20% system time, not sure where it's
going.

No other processes actively running.


This concerns me a bit.


I tried the same thing on a 3 disk ccd array, and it runs much smoother,
w/o the long delays.  Of course, no parity.


The DPT is configured as RAID-5, 128k stripes.  Other than the grief of
installing it, not sure how much benefit there would be to changing this.






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