Lustre discuss - Nov 2007 - Removing an OST

Hi folks,

I have three OSTs running with internal storage, they are only 11% full at
the moment.  I would like to remove one of them for maintenance.

Is this possible at the moment? note that I do not have drbd or HA setup on
these OSTs.  Anyone know the best way to move data of this node and take it
out of the pool cleanly?

I would obviously like the data thats on this OST still available.

Thanks,

Matt
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On Thu, 2007-11-15 at 14:54 +0000, Matt wrote:
> Hi folks,
> 
> I have three OSTs running with internal storage, they are only 11%
> full at the moment.  I would like to remove one of them for
> maintenance.
> 
> Is this possible at the moment? note that I do not have drbd or HA
> setup on these OSTs.  Anyone know the best way to move data of this
> node and take it out of the pool cleanly? 
You need to deactivate (i.e. make it read-only) the OST on the MDS so
that it stops allocating new objects to it.  You then need to use lfs
find to discover all files that have objects residing on that OST and
then simply cp them to a new location and them mv them back to their
original location to force their object recreation on the two active
OSTs and the object deletion on the OST to be removed.

One of our engineers recalls a script being posted to lustre-discuss to
do all of this.  I will leave the searching for you to do.  :-)
> I would obviously like the data thats on this OST still available.
Indeed.  The above process achieves this.

b.