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Date:      Wed, 3 May 2006 14:57:10 +0400
From:      Pavel Merdin <freebsd-fs@merdin.com>
To:        Peter Holm <freebsd-fs@freebsd.org>
Subject:   Re[2]: Stress testing the UFS2 filesystem
Message-ID:  <1408111762.20060503145710@merdin.com>
In-Reply-To: <18034.193.3.141.124.1146642890.squirrel@webmail7.pair.com>
References:  <20060502193900.GA94069@peter.osted.lan> <1541458526.20060503003229@merdin.com> <20060502221306.GD95348@xor.obsecurity.org> <44584421.3000807@cs.tu-berlin.de> <20060503072013.GA2926@xor.obsecurity.org> <18034.193.3.141.124.1146642890.squirrel@webmail7.pair.com>

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Hello ,



Wednesday, May 3, 2006, 11:54:50 AM, you wrote:

>> On Wed, May 03, 2006 at 07:48:17AM +0200, Bj?rn K?nig wrote:
>>> Kris Kennaway schrieb:
>>> >On Wed, May 03, 2006 at 12:32:29AM +0400, Pavel Merdine wrote:
>>> >>Of course I think we could do patches to overcome corrupting panics,
>>> >>but the core FreeBSD team would not accept this, as they are happy
>>> >>with panics and corruptions they make to other filesystems.
>>> >
>>> >Of course not, don't make silly accusations :-)
>>> >
>>> >The problem is much more difficult to solve than "making the panic an
>>> >error return".
>>>
>>> I'm interested in more information about this issue. Do you have a
>>> reference to an old discussion about this topic or do you like to
>>> explain it a little bit further for me (and probably others)?
>>
>> See the URL that Peter provided in his original post.
>>
>> The issue that he is testing is how well the filesystem behaves when
>> you arbitrarily damage it and then run fsck (ideally, fsck should
>> detect all of the damage and repair it).  He seems to have found cases
>> where fsck does not detect and repair the damage, leading to panics at
>> runtime.
>>

> Actually the filesystems mounts without any problems if fsck is run first

That's not a bug in this case. It's a feature. And there is nothing
new in this.
Background  fsck helps saving start time, but it's risky as kernel can
panic if system accesses problematic sector before fsck. So background
fsck should be turned off if one needs reliability (e.g. on servers).


-- 
/ Pavel Merdin






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