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Date: Fri, 22 Jun 2001 08:38:12 -0700 (PDT)
From: Matthew Williams <matthew@informatics.bangor.ac.uk>
To: freebsd-gnats-submit@FreeBSD.org
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Subject: misc/28339: Slow Disk performance on 4.3 (about half that on 4.2)
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>Number:         28339
>Category:       misc
>Synopsis:       Slow Disk performance on 4.3 (about half that on 4.2)
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Fri Jun 22 08:40:01 PDT 2001
>Closed-Date:
>Last-Modified:
>Originator:     Matthew Williams
>Release:        4.3
>Organization:
University of Wales, Bangor. UK.
>Environment:
FreeBSD HOSTNAME.sees.bangor.ac.uk 4.3-REALEASE FreeBSD 4.3-RELEASE #2:
Thu Jun 21 14:45:51 BST  root@HOSTNAME.sees.bangor.ac.uk:/usr/src/sys/compile/P500
 i386
>Description:
We use dd to install Windows onto a partition. Under 4.3 the performance has reduced dramatically.
I have experimented with a binary only install in 4.2 and 4.3 creating a file from
/dev/zero and dd-ing it on to a unmounted raw partition.
Under 4.2 I get an average throughput of about 6MB/sec but under 4.3 this
drops to 3.5MB/sec.

Hardware from dmesg:
pcib0: <Intel 82443BX (440 BX) host to PCI bridge> on motherboard
...
ata: at 0x1f0 irq 14 on atapci0
...
...
ad0: 8223MB <ST38410A> [16708/16/63] at ata0-master UDMA33
acd0: CDROM <CREATIVE CD5233E> at ata1-master using PIO4

>How-To-Repeat:
Create a bin only istallation leaving a spare partition (rad0s1f - in my case) say 100M. Create
a file from /dev/zero (dd count=102400 if=/dev/zero of=/usr/tmp/zero.fil).
Now get iostat running on another console and do the following:
dd bs=256b if=./zeros.fil of=/dev/rad0s1f
A number of runs should get you a good average, the output from dd and iostat should
be the same.

>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted:

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