[Lustre-discuss] Running fsck on disabled ost?

[Oleg Drokin]

Hello!

On Mar 18, 2010, at 1:36 PM, Roy Dragseth wrote:
> Is it possible to fsck on a disabled and drained OST that is mounted readonly?
> We need to fsck an OST and would like to avoid a lengthy downtime while doing 
> it.  My plan is to disable and drain the files from the OST and then remount it 
> read-only before running fsck on the partition.  This would allow for the 
> system being online during this operation instead of hanging on all df 
> commands etc.  But is it at all possible to do it this way?  I would like to 
> avoid any large scale catastrophic events...

You can just disable a specific ost with a command like
lctl conf_param ${fs_name}-OST${NUM}.osc.activate=0

That'd propagate to all clients and even if you bring that ost down later on,
client's won't hang but rather would return an i/o error trying to read/write data
from that OST. df would just stop counting usage (both free and used) from that ost.

After you are done, execute same command, but make it =1 to reenable the OST everywhere.

Bye,
    Oleg