[Lustre-discuss] recover OST data just using ./ROOT/ and ea.bak?

[Andreas Dilger]

On Sep 28, 2009  21:58 -0400, Aaron Knister wrote:
> Doh! Sorry to hear about your dead mdt. I'm no expert but something  
> along the lines of the following may work-
>
> 1. mke2fs -j -J size=400 -I {inode_size} -i 4096 {new mdt dev}
>
> where {inode_size} is at least 512 and possibly larger if the default  
> stripe count is > 10 (inode_size = power_of_2_>=_than(384 + stripe_count 
> * 24))
>
> 	tune2fs -O dir_index {new mdt dev}
>
> 2. Mount the new mdt as ldiskfs (mount -o ldiskfs) at say /mnt/mdt
>
> 3. Restore ROOT and your eas.  (unmount the mdt)
>
> 4. Run tunefs.lustre --fsname={fsname} --mdt --mgs --writeconf {new mdt 
> dev } on the new mdt
>
> 5. Shutdown all your osts
>
> 6. Run tunefs.lustre --writeconf on your osts
>
> 7. Pray to the lustre gods for mercy
>
> 8. Mount your mdt as lustre (mount -o lustre)
>
> 9. Re-mount your osts and hope for the best
>
> Hopefully one of the lustre experts on this list will comment on the  
> above with a "yep that'll work" or "you gotta be crazy to do that"

It at least has a chance to work.  The majority of the Lustre-specific
files on the MDT will be (re-)created at "first" mount, and will fetch
the object IDs from the OSTs to recreate the entries in the lov_objids
file.

> On Sep 28, 2009, at 1:32 PM, Matt Franks wrote:
>> Ok, here's a good one...
>>
>> I have a lustre set up with version 1.8. Its has a combo mdt/mgs on  
>> one machine and three OSSs with a couple of OSTs on each.
>>
>> The array that the mdt/mgs was on died and decided to stay dead,  
>> taking its data with it. But, I thought, no problem I have my file  
>> level backup that I did a couple of days ago. But owing to a typo in  
>> the script I ran, I only got the tar and getfattr of the ROOT  
>> directory, rather than the whole volume.
>>
>> My question to the lustre public is.. is it possible to recover the  
>> data on the OSTs using this? If so, can anyone lend any pointers? (If, 
>> in theory its not possible, I'll stop banging my head against the wall 
>> and move on)
>>
>> Any advice appreciated!
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>

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Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.