My setup: I have 2 hosts, and 2 shards each. Host1 has 2 shards, and is the master of the replicas host2 has the secondaries of the 2 shards. . host1: shard1 (repset1),shard2 (repset2) host2: shard1 (repset1),shard2 (repset2) There's also a 3rd host that acts as arbitrer. I have 50 threads writing randomly to both shards (using a hash)…