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Date:      Tue, 17 Jul 2001 17:00:07 -0700 (PDT)
From:      Ian Dowse <iedowse@maths.tcd.ie>
To:        freebsd-bugs@FreeBSD.org
Subject:   Re: i386/29045: Heavy disk usage causes panic in ffs_blkfree 
Message-ID:  <200107180000.f6I007x12428@freefall.freebsd.org>

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The following reply was made to PR i386/29045; it has been noted by GNATS.

From: Ian Dowse <iedowse@maths.tcd.ie>
To: Bill Moran <wmoran@iowna.com>
Cc: freebsd-gnats-submit@FreeBSD.org
Subject: Re: i386/29045: Heavy disk usage causes panic in ffs_blkfree 
Date: Wed, 18 Jul 2001 00:53:35 +0100

 In message <3B54C17D.F31029C2@iowna.com>, Bill Moran writes:
 >Errr ... I tried, but frame 2 considers those symbols undefined.
 >Did I misunderstand?
 
 Whoops, no I did. It was frame 3 that should contain these symbols,
 but now that you have an easier way to get corruption, that vmcore
 is of less interest.
 
 >I ran two tests during the "make buildworld" (one right after the other)
 >I ran a diff on the two resultant files and Lo and Behold! there are a
 >slew of differences in the hashes.
 
 Ok, that's progress anyway, even if it's not progress in the most
 desirable direction... I think you can pretty much rule out any
 filesystem bugs here; either the hardware is bad (disk, ATA
 controllers, RAM etc) or possibly there is something the ATA driver
 isn't doing right, such as missing a workaround for a known hardware
 bug.
 
 One thing that would be very useful is if you can collect a number
 of samples of "good" and "corrupted" versions of the same file.
 That may be tricky to do, because right now we don't know anything
 about where the data is being corrupted. Maybe try to make 2 copies
 of lots of files to another system, and then md5 each and look for
 differences.
 
 When you find two differing versions of the same file, say "file.good"
 and "file.bad", get a hex dump of the differences:
 
 	hd file.good > file.good.hd
 	hd file.bad > file.bad.hd
 	diff -u file.good.hd file.bad.hd
 
 Do this for a few files and look for patterns; there might be
 something that would suggest where the corruption is happening.
 It would also be well worth trying swapping hardware components
 to see if you can isolate the cause.
 
 Ian
 

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