Hello, we've notice recently that the moveChunk directory will rapidly start using all of it's available disk space. Looking through the logs, we saw errors of Sun Jan 5 09:43:14 [migrateThread] ERROR: migrate failed: E11000 duplicate key error index: blah.$ownerid_1_docname_1_osvcname_1 dup key: { : "11446719", : "app.json", : "blah" }. We recently upgraded to 2.2.6 from 2.2.4 though I am not sure if that is relevant.

When the disk fills, mongod crashes and fails over to the secondary. After clearing out the moveChunk dir, the partner (now primary node) will have the same behavior the next day. If we remove the offending duplicate key, the issue stops.