[Lustre-discuss] questions about an OST content

Bob Ball ball at umich.edu
Sun Nov 7 11:32:14 PST 2010


Hi, Andreas.

Tomorrow, we will redo all 8 OST on the first file server we are 
redoing.  I am very nervous about this, as a lot is riding on us doing 
this correctly.  For example, on a client now, if I umount one of the 
ost, without first taking some (unknown to me) action on the MDT, then 
the client will hang on the "df" command.

So, while we are doing the reformat, is there any way to avoid this 
"hang" situation?

Is the --index=XX argument to mkfs.lustre hex, or decimal?  Seems from 
your comment below that this must be hex?

Finally, does supplying the --index even matter if we restore the files 
below that you mention?  That seems to be what you are saying.

Thanks much,
bob

On 11/6/2010 11:09 AM, Andreas Dilger wrote:
> On 2010-11-06, at 8:24, Bob Ball<ball at umich.edu>  wrote:
>> I am emptying a set of OST so that I can reformat the underlying RAID-6
>> more efficiently.  Two questions:
>> 1. Is there a quick way to tell if the OST is really empty?  lfs_find
>> takes many hours to run.
> If you mount the OST as type ldiskfs and look in the O/0/d* directories (capital-O, zero) there should be a few hundred zero-length objects owned by root.
>
>> 2. When I reformat, I want it to retain the same ID so as to not make
>> "holes" in the list.  From the following information, am I correct to
>> assume that the id is 24?  If not, how do I determine the correct ID to
>> use when we re-create the file system?
> If you still have the existing OST, the easiest way to do this is to save the files last_rcvd, O/0/LAST_ID, and CONFIGS/*, and copy them into the reformatted OST.
>
>> /dev/sdj              3.5T  3.1T  222G  94% /mnt/ost51
>>   10 UP obdfilter umt3-OST0018 umt3-OST0018_UUID 547
>> umt3-OST0018_UUID           3.4T        3.0T      221.1G  88%
>> /lustre/umt3[OST:24]
>>   20 IN osc umt3-OST0018-osc umt3-mdtlov_UUID 5
> The OST index is indeed 24 (18 hex). As for /dev/sdj, it is hard to know from the above info. If you run "e2label /dev/sdj"  the filesystem label should match the OST name umt3-OST0018.
>
> Cheers, Andreas
>



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