[Lustre-discuss] advice on OST journals in OSS failover pairs

[Oleg Drokin]

Hello!

On Feb 13, 2011, at 6:54 PM, Samuel Aparicio wrote:

> We are planning OSS failover pairs for a lustre deployment, the question of external journals comes up.
> testing showed that for our applications having an external journal for the OSTs provides a worthwhile increase in performance.
> 
> For a failover pair this presumably means that the OST journals should have to reside on an external storage target that each OSSs pair can see?

Yes, basically you need two LUNs visible on both nodes per OST. One for the data and one for the journal.

> Or would the MDS journal take over in the case of an OSS switchover?

MDS journal is just for the MDS, it has nothing to do with OSTs.

Also you might want try async journal commits (+ make your journals big) to see if that improves your performance in a similar way to an external journal.

Bye,
    Oleg