"Heartbeat for volume [datastore name] with UUID [uuid] timed out on host [hostname]"
In the world of VMware vSphere, few alarms evoke as much immediate concern from storage and virtualization administrators as the dreaded . This error appears as a triggered alarm in the vCenter Server, often accompanied by a yellow (warning) or red (error) status on one or more ESXi hosts. While it might sound cryptic at first, the message carries a clear implication: your ESXi host has lost communication with a VMFS datastore, at least temporarily. esx.problem.vmfs.heartbeat.timedout
When this issue occurs, you will typically see an entry in the vCenter tab or in the Events section of a specific host. The full message resembles: "Heartbeat for volume [datastore name] with UUID [uuid]
: Suggests a flood of I/O errors is occurring. When this issue occurs, you will typically see
| Cause | Solution | |-------|----------| | | Rescan storage adapters: esxcli storage core adapter rescan --all | | HBA/Driver issue | Update to VMware-certified firmware/driver version. | | FC Zoning/ISL | Verify zone membership, check ISL utilization and errors. | | iSCSI network loss | Enable Jumbo Frames consistently, use separate vSwitch/VMkernel ports, enable port binding. | | Storage array overload | Throttle snapshots, balance load, upgrade array firmware. | | APD handling | Set advanced option: VMFS.APDHeartbeatTimeout (default 140s). Consider setting VMFS.FailVolumeOpenIfAPD for faster failure. |
This timeout is rarely a bug in ESXi itself and is typically a symptom of underlying infrastructure issues: