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Date:      2 May 2002 14:25:49 -0000
From:      atk2@arctic.org
To:        freebsd-stable@FreeBSD.ORG
Subject:   dd of=/dev/eide_drive bs=8192 if=/dev/mem kills system
Message-ID:  <20020502142549.21601.qmail@twinlark.arctic.org>

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I have 4.5-stable (updated it last night to get the ata 133 support for
my disk drive). I was doing a bit of crude benchmark and used
dd if=/dev/ad0s2e bs=8192 of=/dev/null to test read speed
(iostat -c 100 indicates about 40MB/sec sustained (i.e., not cache) - if
 it is accurate)

Anyways I then tried to test write speed with

dd of=/dev/dev/ad0s2e bs=8192 if=/dev/mem

and the system hanged. This was an unmounted slice - yea I know if it worked 
it would have killed the slice - but the slice is unused so I didn't care). I'm
not overly concern that the above killed the system as it isn't needed for 
daily use -- just noting it in case it is a kernel bug... (note kernel didn't
panic - it hanged - I waited about 5 minutes then did a reset -- nothing 
responded during that time including mouse (was running X) and hdd light on
case was off)

Alan

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