Unplanned device loss is a condition that occurs when your ESXi host permanently loses connection to a storage device.

Although the ESXi host cannot determine the reason for a device loss, the host supports the loss detection. When the device becomes permanently unavailable, ESXi receives sense codes from storage arrays and recognizes that the device is permanently lost, not just temporarily unavailable. ESXi marks the device as not connected and a warning about the device being permanently unavailable appears in the VMkernel log file.

Typically, unplanned device loss is unintentional and can occur when a storage device is unmapped, removed, or its unique ID changes, or when there is an unrecoverable hardware error.

If you experience an unplanned device loss condition, you must unmount any related datastores and perform a storage rescan to remove the persistent information associated with the device. See the following topics:

To verify the status of the device, see Check the Connection Status of a Storage Device.

To unmount a datastore, see Unmount VMFS or NFS Datastores.

To perform a rescan, see Perform Storage Rescan.