Datastore cannot be unmounted/deleted from vCenter server.

Products

• VMware vCenter Server

Issue/Introduction

Symptoms:

• Datastore cannot be unmounted/deleted from vCenter server. User get the following error when the unmount is tried.

• It is confirmed that the datastore is not in use. There are no VM's or VM template reside in the datastore. Storage DRS does not manage the datastore. Storage I/O Control is disabled for this datastore. No vCLS VM registered and the datastore is not used for the coredump partition. 

Environment

VMware ESXi 7.x
VMware ESXi 8.x

Cause

The unmount is failing because metadata corruption is noticed on the concerned datastore which the user is trying to unmount. The following excerpts can be seen from the vmkernel and vobd logs.

YYYY-MM-DDT##:##:##.###Z cpu9:1001390796)WARNING: Res3: StatVMFS6:7090: Volume __DATASTORE_UUID__("__DATASTORE_NAME__") might be damaged on the disk. Resource cluster metadata corruption has been detected.

Because of the metadata corruption, the unmount calls are not going through and the process failed.

Resolution

Based on the nature of corruption the user can use VOMA tool to fix the corruption and unmount the datastore again.
Please contact VMware support team to perform metadata check, refer to KB: Using vSphere On-disk Metadata Analyzer, on how to use VOMA tool.

Note: Metadata inconsistency in the VMFS volume might be fixed or not depending on the nature and extent of corruption. It depends on case to case basis and customer may decide to restore the datastore from backup.

Workaround:

In such scenario, the storage device which hosts the corrupted datastore can be detached physically from the storage array and post that the unmount command can be tried followed up with the storage rescan to unmount the datastore.