[lustre-discuss] Mounting lustre with some OST missing

Paul Edmon pedmon at cfa.harvard.edu
Thu Dec 13 06:58:46 PST 2018

In the past for these situations I've used the lctl deactivate command 
to deactivate specific OST's.  That way you can still use the system 
while you repair.  This page has the lctl command in it.


-Paul Edmon-

On 12/13/18 5:24 AM, Tung-Han Hsieh wrote:
> Dear All,
> I am asking whether it is possible to mount lustre when some of the
> OSTs are missing.
> The situation is following. We have some old systems running Lustre
> version 1.8.8. One of the file server which contains several OSTs
> were broken, and need some time to repair. In the meantime, we are
> urgent to copy some data out of the lustre file system in order
> to continue our works. But without the OSTs of that broken file
> server, presumably we cannot mount the lustre file system.
> Is there a trick to temporarily mount the lustre file system even
> read only ? I know that we can remove the OSTs in the broken file
> server by running these command in the MDT server:
> lctl conf_param foo-OSTXXXX.osc.active=0
> Then we are able to mount it. But when the file server is repaired,
> could we safely add its OSTs back to the lustre file system and
> recover all the data in these OSTs ?
> If the answer to the previous question is "yes", then what will
> happen if, before the broken file server coming back, the MDT server
> accidently needs reboot ? In this case can we still add back these
> OSTs safely when that file server is repaired ?
> Or, is there a better way to temporarily mount it in read only ?
> Thank you very much for your help.
> T.H.Hsieh
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