[Lustre-discuss] e2scan wrong file list mtime/ctime

[Andreas Dilger]

On 2009-12-23, at 04:11, Andrea Pieretti wrote:
> Dear Andreas, sorry for the delay,
> I work with Miguel, so i'll write for him.
>
> We have one question,
> is it possible (safe) to use debugfs on a mounted Lustre filesystem?

Yes, this is safe unless you open the filesystem with "-w" (write mode).
Without that you shouldn't be able to modify the filesystem, and it is
safe.

> Andreas Dilger wrote:
>> On 2009-12-16, at 06:28, Miguel Molowny Lopez wrote:
>>
>>> we are running lustre 1.8.1.1 on our storage cluster based on IB.
>>>
>>> We are building a "bulldozer" for a scratch area and we have found  
>>> an
>>> odd behaviour in the e2scan utility (maybe a bug or a ... "defined
>>> behaviour" we don't know about).
>>>
>>> We have reproduced this behavior several time and we are having  
>>> these
>>> results:
>>> - we run e2scan on the MDT to have the files newer than 3 days ago:
>>>  command line used was like:
>>>    * e2scan -l -N '2009-12-13' /dev/mapper/mdt
>>>    or:
>>>    * e2scan -l -n /tmp/file.timestamp /dev/mapper/mdt
>>>      where file.timestamp has been created with the date of
>>>      3 days ago using touch
>>>  The result is sorted and saved in a file called: 3daysago.list
>>> - we then run another e2scan looking for files newer than 2 days ago
>>>  using the same command line and the result is sorted and saved in
>>>  a file called: 2daysago.list
>>>
>>> The problem is that there are files whose last modification time is
>>> before the date at which we run the two e2scan commands (they were  
>>> not
>>> modified during the run of e2scan) _BUT_ they appear only in the  
>>> list
>>> 3daysago.list. Here is an example:
>>>
>>> - first run of e2scan at: Dec 15 16:20 (produce list 3daysago.list)
>>> - second run of e2scan at: Dec 15: 16:50 (produce list  
>>> 2daysago.list)
>>> - file: /scratch/foobar.txt has mtime=ctime = Dec 14 03:19
>>>
>>>  This file is still on filesystem after the run of the two e2scan  
>>> cmd
>>> well, this file appears only in the 3daysago.list. And this happen  
>>> for
>>> a _LONG_ list of files.
>>>
>>
>>
>> This is definitely odd.  It is worthwhile to check what the timestamp
>> is on the MDS, via "debugfs -c -R 'stat foobar.txt'", in addition to
>> checking via "stat /scratch/foobar.txt" in the filesystem.
>>
>> Cheers, Andreas
>> --
>> Andreas Dilger
>> Sr. Staff Engineer, Lustre Group
>> Sun Microsystems of Canada, Inc.
>>
>> _______________________________________________
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>> Lustre-discuss at lists.lustre.org
>> http://lists.lustre.org/mailman/listinfo/lustre-discuss
>>
>
> -- 
> +-------------------------------------------------------
> +  Andrea Pieretti
> +  C.A.S.P.U.R.,
> +  Via dei Tizii, 6b
> +  00185 Roma ITALY
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> +  mob: +39-328-4280841
> +  fax: +39-06-4957083
> +  e-mail: a.pieretti at caspur.it
> +  http://www.caspur.it
> +-------------------------------------------------------
> +
> +          "Nitwit! Blubber! Oddment! Tweak!"
> +
> +             Albus Percival Wulfric Brian Dumbledore
> +-------------------------------------------------------
>
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Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.