Hi,

I have some problems with my ceph monitor nodes in my Cluster.
I had 5 mons in the cluster. On all 5 nodes the leveldb store grew up to 
about 80 – 90 GB in size. To get rid of it I triggerd a compaction with 
the following command on one node.
  ceph tell mon.d compact

The Monitor compacted his data to about 5 GB. After this the mon tried to synchronize his data with the other mons. And start my problems.
After a short time (20 – 30 sec) of streaming data from another mon node 
The stream breaks and further the sender reads oviously all the other 
data in his store with maximum speed. At this point the cluster lost his 
leader and trying to elect a new one. The leader election only works if 
the reading of the data is done.
I tried to remove the mon from the cluster completly and rejoin it as a 
new one but while syncing I experience the same issue. So currently the 
cluster has only 4 Mons.
While further investigation and testing I lost another mon which wants 
to sync data after starting with the same behavior.
It seems the Node which streams data while syncing is in stress with 
reading and sending data. I tried to limit the network bandwith of the 
joining node to reduce the load. I also tried to set ionice -c3 on the 
process which does all the disk IO while reading. But nothing helped.
Because the cluster is productive I don't want to expermient further 
more without knowing what's going on.
Does anyone have any ideas what's going on and how I can try to fix this?

I am using ceph version 0.67.11 (bc8b67bef6309a32361be76cd11fb56b057ea9d2)
5 Monitor Nodes with SSD as leveldb store
24 OSD Hosts with 1416 OSDs

Thank you
Manuel

--
Manuel Lausch

Systemadministrator
Cloud Backend Services

1&1 Mail & Media Development  & Technology GmbH | Brauerstraße 48 | 76135 
Karlsruhe | Germany
Phone: +49 721 91374-1847
E-Mail: manuel.lau...@1und1.de | Web: www.1und1.de

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Geschäftsführer: Frank Einhellinger, Hans-Henning Kettler, Jan Oetjen


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