HA datastore heartbeats prevent host isolation
What are datastore heartbeats?\n\nThe host-X-hb (where X is the host\u2019s MOID) is Located on each heartbeat datastore, this file is used to check for slave liveness through the heartbeat datastore. \nThis file is checked by the master host if the master loses network heartbeats from the slave.\n \nFor VMFS datastores, the vSphere HA agent locks this file with an exclusive lock and relies on the VMkernel heartbeat to indicate liveness. \nFor NFS datastores, vSphere HA periodically updates the time stamp to this file to indicate liveness.\n\nThe host-X-poweron (where X is the host\u2019s MOID) is a per-host file that contains the list of all virtual machines that are powered on. This file is used as a communication channel if a management network outage occurs. Isolated slaves use this file to tell the master that it is isolated as well as to tell the master which virtual machines it has powered off.\n\nThe master host must determine whether the slave host:\n\n\u2022 Actually crashed \n\u2022 Is not responding because of a network failure \n\u2022 The HA agent is in an unreachable state\n\nThe absence of both a network and datastore heartbeat indicates full host failure. Datastores are used as a backup communication channel to detect virtual machine and host heartbeats. Datastore heartbeats are used to make the distinction between a failed, an isolated or a partitioned host.