Cannot delete datastore with Error "An error occurred during host configuration. Operation failed, diagnostics report: Not a known device"

Products

• VMware vCenter Server

Issue/Introduction

When attempting to remove an Inaccessible datastore you get the following error. 

"An error occurred during host configuration. Operation failed, diagnostics report: Not a known device"

Environment

VMware vCenter (all versions)

Cause

The backing storage for the datastore has been removed rendering the datastore inaccessible in vCenter.  When the delete operation is run it can no longer find the disk to be removed this results in failure.  

Resolution

Rescan the storage on the hosts where the inaccessible datastore is present.  

A rescan of storage devices is needed when a storage device has been added, removed, or changed from the array. The rescan in the vSphere Client, by default, combines the rescan for new LUNs and removal of retired ones with the detection of new VMFS datastores.

Reference KBs

Performing a rescan of the storage on an ESXi host 

Unable to remove inaccessible datastore entry from vCenter

Ensure to follow proper process for removing a datastore as outlined via Remove VMFS Datastores

Additional Information

This error can also occur when iSCSI targets are still configured for the datastore backing device. If the iSCSI targets are no longer needed, remove the targets from the ESXi host storage configuration.