[lustre-discuss] Do not recreate OST objects on OST replacement

Andreas Dilger adilger at whamcloud.com
Thu Sep 12 02:45:05 PDT 2019

On Sep 10, 2019, at 10:23, Degremont, Aurelien <degremoa at amazon.com<mailto:degremoa at amazon.com>> wrote:


When an OST dies and you have no choice but replacing it with a newly freshly formatted one (using mkfs --replace), Lustre runs a resynchronization mechanisms between the MDT and the OST.
The MDT will sent the last object ID it knows for this OST and the OST will compare this value with its own counter (0 for a freshly formatted OST).
If the difference is greater than 100,000 objects, it will recreate only the last 10,000, if not, it will recreate all the missing objects.

I would like it to avoid recreating any objects. The missing ones are lost and just start recreating new ones. Is there a way to achieve that?

It isn't currently possible to completely avoid recreating these objects.  Normally it isn't a huge problem, given the size of normal OSTs.  This is done to ensure that if the MDS has previously allocated those objects there will be objects available for the clients to write to them. LFSCK can be used to clean up these orphan objects if they are not in use.

Cheers, Andreas
Andreas Dilger
Principal Lustre Architect

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