There are a number of internal Ceph tools that can be used to help diagnose a slow performance. The most useful command for investigating slow performance is dumping current in-flight operations, which can be done with a command such as the following:

sudo ceph daemon osd.x dump_ops_in_flight

This will dump all current operations for the specified OSD and break down all the various timings for each step of the operation. Here is an example of an inflight IO:

From the previous example IO, we can see all the stages that are logged for each operation; it is clear that this operation is running without any performance problems. However, in the event of slow performance, you may see a large delay between two steps, and directing your investigation into this area may lead you to the route cause.