[Lustre-discuss] Could I restore OST without EA ?

Dilger, Andreas andreas.dilger at intel.com
Wed Mar 11 22:42:33 PDT 2015

On 2015/03/11, 12:57 AM, "Tung-Han Hsieh" <thhsieh at twcp1.phys.ntu.edu.tw>

>Dear Dilger and All,
>Thanks very much for your helpful information.
>Now after a long delay, our corrupted data in that OST is rescued
>by a company. We have prepared a new file server, with rebuit RAID
>and Lustre file system (OST), and sent it the the data rescue company
>to copy the data back.
>It seems that > 99.9% data files in that OST can be retrived and
>are in their correct O/0/d*/ directories. So later we will try to
>put it back to our Lustre filesystem, and see whether only the EA's
>of MDT could access these files or not.
>But here we encounter a problem. Since the facilities of the data
>rescue company is Windows based, they told me that the most they
>can do is to recover the data files, but without all the informations
>of their corresponding inodes (they don't have the tools to do that).
>That means, the owners, creation/modification times, permissions, and
>EA's of all the files can not be recovered. Now we hope that without
>EA's these files can still be accessable. But we still have to fix
>the problems of the owners, creation times, and permissions.

None of these attributes are needed for the OST to work.

>Is it possible that, using the EA's of MDT, could we figure out the
>location of each file ? I mean, could we find, for example, the
>location of
>	MDT:  /ROOT/the/full/path/to/a/file
>that is in which OST and which file ? Then we can manually fix their
>owner, creation / modification time, and permission manually, according
>to those of the corresponding file in MDT.

With Lustre 2.6 and later, LFSCK will automatically repair these
and without them it is not very easy to do this.

Cheers, Andreas

>Thank you very much for your great help.
>Best Regards,
>On Fri, Feb 13, 2015 at 06:09:46PM +0000, Dilger, Andreas wrote:
>> On 2015/02/12, 2:47 AM, "Tung-Han Hsieh" <thhsieh at twcp1.phys.ntu.edu.tw>
>> wrote:
>> >We have a Lustre filesystem (version 1.8.8) in our lab, which
>> >contains several about 20 OSTs and only one MDT. Recently one
>> >of our file server got serious crashed. It contains 4 OSTs
>> >stored in RAID 5. We sent the file server to data rescue company.
>> >They told me that they can rescue all the data files, but the EA
>> >of these files may be lost.
>> >
>> >In the Lustre Operational Manual, I learn that to restore the
>> >MDT in filesystem level, we should restore both all the files
>> >as well as their EAs. But how about OST ? Could we restore it
>> >without the EA of files ? I mean, without running this ?
>> >
>> >	setfattr --restore=ea.bak
>> >
>> >If very fortunately I can restore it without EA, what is the
>> >next I should do to bring the whole filesystem to be in a
>> >consistant state ?
>> That depends on whether there is other corruption in the OST
>> You do not need the OST EAs for normal usage, but if the OST directory
>> structure is corrupted then the EA data is useful to rebuild the OST
>> directory structure (use ll_recover_lost_found_objs to move objects from
>> lost+found/ into O/0/d*/ directories).
>> Cheers, Andreas
>> -- 
>> Andreas Dilger
>> Lustre Software Architect
>> Intel High Performance Data Division
>lustre-discuss mailing list
>lustre-discuss at lists.lustre.org

Cheers, Andreas
Andreas Dilger

Lustre Software Architect
Intel High Performance Data Division

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