From owner-freebsd-stable  Mon Mar 12 12:36:39 2001
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From: Soren Schmidt <sos@freebsd.dk>
Message-Id: <200103122036.VAA99695@freebsd.dk>
Subject: Re: Disk I/O problem in 4.3-BETA
In-Reply-To: <200103122031.f2CKVRs19327@ptavv.es.net> from Kevin Oberman at "Mar 12, 2001 12:31:27 pm"
To: oberman@es.net (Kevin Oberman)
Date: Mon, 12 Mar 2001 21:36:27 +0100 (CET)
Cc: mobile@FreeBSD.ORG, stable@FreeBSD.ORG
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It seems Kevin Oberman wrote:
> I'm not too sure if this belongs in mobile or stable. I reported the
> problem last week, but have seen no comments. Either it's something
> unique to my system (or my hardware) or people have not been doing
> large disk copy operations.
> 
> My disk I/O performance has tanked after a cvsup on March 1.
> Subsequent updates have not made a difference.

Some of this might be due to write caching being turned off as
default now, this was done due to "popular demand" because
write caching can hose your filesystem on a power outage. 

> Specifics: System ran normally until the March 1 cvsup. The prior
> cvsup was February 24.  
> 
> Prior to March 1 I could dd a 4 GB slice in 580 seconds (or a bit
> under 10 minutes).  After March 1 the same exact command took just
> under 40 minutes to complete. The same was seen copying a 2 GB
> slice. It increased from 5 minutes to 20 minutes. No kernel
> configuration changes were made.

This is worse than expected, try to use option ATA_ENABLE_WC
and see what gives, if its not back to normal we have to look elsewhere.

-Søren

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