"Clustered VMDK Support cannot be enabled on iSCSI datastores in VMware vCenter 8.x

Products

• VMware vCenter Server

Issue/Introduction

All data has been migrated from the old storage to the new storage then trying to enable clustered vmdk on the datastore.

Environment

VMware vCenter 8.x
VMware ESXi 8.x

Cause

Clustered VMDK feature is unsupported with iSCSI protocol and its a product limitation.

Resolution

1. Fibre Channel (FC) and vVOL storage protocol is supported for clustered VMDK
2. Instead of Clustered VMDK use an RDM for iSCSI protocol 

Additional Information

https://techdocs.broadcom.com/us/en/vmware-cis/vsphere/vsphere/8-0/setup-for-windows-server-failover-clustering/cluster-virtual-machines-across-physical-esxi-hosts/clustered-vmdk-support-for-wsfc/limitations-of-clustered-vmdk-support-for-wsfc.html