[ceph-users] slow MDS requests [Solved]

[Alfredo Daniel Rezinovsky]

I had a lot of "slow MDS request" (MDS, nos OSD) when writing a lot of 
small files to cephfs.

The problem was an I/O stuck when flushing XFS buffers. I had the same 
problem in other (non ceph) xfs systems when asking for a lot of inode 
operations (rm -rf for example).

The solution was to destroy the filestore (xfs) OSDs and recreate them 
in bluestore. Is a slow process. First you have to stop the OSDs, wait 
for rebalancing, destroy, recreate, and go on with the next OSD. It took 
a 10 days to recreate 8 OSDs with 3Gb each (In production, with the RBD 
and CEPHFS services in use).

Hope this helps.

--
Alfredo Daniel Rezinovsky
Director de Tecnologías de Información y Comunicaciones
Facultad de Ingeniería - Universidad Nacional de Cuyo

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