Hello everybody! I test the performance of ceph cluster using different osd_op_num_shards and different osd_op_num_threads_per_shard configuration. And I found that using multi-thread(with a single shard) can get the same improvement of performance with multi-shard. However, the document of ceph osd config(http://docs.ceph.com/docs/master/rados/configuration/osd-config-ref/#caveats) said that using lower shard number may have deleterious effects. I want to know what the deleterious effects are. Thanks for the assistance! Fibird chaoyanglius@gmail.com