[Lustre-discuss] Using drbd: reformat disk or only sync ?

Andreas Dilger adilger at sun.com
Sat Nov 21 00:25:45 PST 2009


On 2009-11-20, at 19:36, Dam Thanh Tung wrote:
> We just started drbd from OST (which has been rebuild RAID  
> partition) and connect with drbd on an working OST. Everything was  
> fine and the synchronization completed without any error report.  
> But, when we mount this backup OST in to our system, some of web  
> client can't connect to it ( MDS and some others can ) and after a  
> short time, in that OST message log, we see many error report like  
> this :
>
> Nov 19 19:59:36 OST6 kernel: LDISKFS-fs error (device drbd6):  
> ldiskfs_lookup: unlinked inode 159588368 in dir #261333022
>
> Nov 19 19:59:36 OST6 kernel: LustreError: 3893:0:(filter_lvb.c: 
> 90:filter_lvbo_init()) lustre-OST0006: bad object 996598/0: rc -2

It sounds to me like you are trying to mount the "backup OST" at the  
same time as the "primary OST"?  That is definitely NOT how Lustre  
works.  You should stop that, as it will cause serious filesystem  
corruption if you are doing that.

The backup OST should only be mounted when the primary has failed  
(preferably when the primary is powered down via STONITH so that there  
is no chance it will still modify the filesystem).  This is normally  
controlled by HA software like Heartbeat or similar.
> In order to using drbd as back up solution as i described above, do  
> we need to reformat disk before synchronize data or just sync it  
> directly?
>

I haven't used DRBD myself, but I believe that it should NOT require  
formatting a device before using DRBD on it.  However, there would  
need to be an initial synchronization to copy all of the data from the  
primary copy to the backup.  DRBD is just doing a block-level copy of  
one device to another, it doesn't know anything about the filesystem.

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




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