[Lustre-discuss] [HPDD-discuss] Recovering a failed OST

Bob Ball ball at umich.edu
Mon May 19 11:24:22 PDT 2014

Oh, better still, as I kept looking, and the low-level panic retreated, 
I found this on the mdt:

[root at lmd02 ~]# lctl get_param osc.*.prealloc_next_id

So, unless someone tells me that I am way off base, I'm going to proceed 
with the assumption that this is a valid starting point, and proceed to 
get my file system back online.


On 5/19/2014 2:05 PM, Bob Ball wrote:
> Google first, ask later.  I found this in the manuals:
>       26.3.4 Fixing a Bad LAST_ID on an OST
> The procedures there spell out pretty well what I must do, so this 
> should be relatively straight forward.  But, does this comment refer 
> to just this OST, or to all OST?
> *Note - *The file system must be stopped on all servers before 
> performing this procedure.
> So, is this the best approach to follow, allowing for the fact that 
> there is nothing at all left on the OST, or is there a better short 
> cut to choosing an appropriate LAST_ID?
> Thanks again,
> bob
> On 5/19/2014 1:50 PM, Bob Ball wrote:
>> I need to completely remake a failed OST.  I have done this in the 
>> past, but this time, the disk failed in such a way that I cannot 
>> fully get recovery information from the OST before I destroy and 
>> recreate.  In particular, I am unable to recover the LAST_ID file, 
>> but successfully retrieved the last_rcvd and CONFIGS/* files.
>> mount -t ldiskfs /dev/sde /mnt/ost
>> pushd /mnt/ost
>> cd O
>> cd 0
>> cp -p LAST_ID /root/reformat/sde
>> The O directory exists, but it is empty.  What can I do concerning 
>> this missing LAST_ID file?  I mean, I probably have something, 
>> somewhere, from some previous recovery, but that is way, way out of 
>> date.
>> My intent is to recreate this OST with the same index, and then put 
>> it back into production.  All files were moved off the OST before 
>> reaching this state, so nothing else needs to be recovered here.
>> Thanks,
>> bob
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