Symptoms for failed heartbeat_checks can include OSDs being wrongly marked down and possibly out. Hearbeat checks are sent to peers every osd_heartbeat_interval seconds (6 by defailt). If no response has been received in a span of 20 seconds, the OSD will determine the peer to be down and report this to the monitor. If the monitor receives osd_heartbeat_interval (3) reports, the OSD will be ma...