Re: [testcase] test your fs/storage stack (was Re: [patch] ext2/3:document conditions when reliable operation is possible)

From: Pavel Machek
Date: Sat Sep 05 2009 - 06:33:33 EST

On Fri 2009-09-04 07:49:34, Ric Wheeler wrote:
> On 09/04/2009 03:44 AM, Rob Landley wrote:
>> On Thursday 03 September 2009 09:14:43 jim owens wrote:
>>> Rob Landley wrote:
>>>> I think he understands he was clueless too, that's why he investigated
>>>> the failure and wrote it up for posterity.
>>>>> And Ric said do not stigmatize whole classes of A) devices, B) raid,
>>>>> and C) filesystems with "Pavel says...".
>>>> I don't care what "Pavel says", so you can leave the ad hominem at the
>>>> door, thanks.
>>> See, this is exactly the problem we have with all the proposed
>>> documentation. The reader (you) did not get what the writer (me)
>>> was trying to say. That does not say either of us was wrong in
>>> what we thought was meant, simply that we did not communicate.
>> That's why I've mostly stopped bothering with this thread. I could respond to
>> Ric Wheeler's latest (what does write barriers have to do with whether or not
>> a multi-sector stripe is guaranteed to be atomically updated during a panic or
>> power failure?) but there's just no point.
> The point of that post was that the failure that you and Pavel both
> attribute to RAID and journalled fs happens whenever the storage cannot
> promise to do atomic writes of a logical FS block (prevent torn
> pages/split writes/etc). I gave a specific example of why this happens
> even with simple, single disk systems.

ext3 does not expect atomic write of 4K block, according to Ted. So
no, it is not broken on single disk.

>> The LWN article on the topic is out, and incomplete as it is I expect it's the
>> best documentation anybody will actually _read_.

Would anyone (probably privately?) share the lwn link?
(cesky, pictures)
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