When you try to configure a local datastore as RDM in VMware ESXi 6.5, local storage devices are not available to provision the datastore.
Local controllers not meeting the hardware requirements are often the reason of problems during the local datastore configuration.
Configure a local datastore
To configure a new datastore, you need to access vCenter Server or local ESXi. Open VMWare vSphere Web Client and enter the correct credentials to access the vCenter Server then click Login.
Select an ESXi host and go to Configure > Storage Devices. The attached local HDDs are visible in the list and available to the system.
To create a local datastore, go to Configure > Datastores and click the Create a new datastore icon.
Select VMFS option as datastore type and click Next.
Local storage devices to provision the new datastore are not visible in the list even the system recognized them as shown in the Storage Devices tab.
By default, local storage devices are disabled as potential RDM candidates on an ESXi host due to most existing local controllers not meeting the hardware requirements to correctly address and communicate with an RDM disk.
Enable local RDM
To enable local storage devices, select the ESXi to configure and go to Configure > Advanced System Settings tab and click Edit button.
Search for RdmFilter.HbalsShared parameter to manage local storage devices visibility. By default this parameter is Enabled.
Disable the parameter by removing the flag in the Enable option and click OK to confirm.
Click Rescan all storage adapters icon to discover new storage devices.
Click OK to proceed.
Right click the host and select Power > Reboot option to reboot the ESXi.
When you run the datastore creation wizard once again, local HDDs are now visible in the list.
Specify the VMFS version to use then click Next.
Specify the datastore details then click Next.
Click Finish to save the configuration and to create the new datastore.
The local datastore has been created successfully.
In case of trouble, make sure you have a suitable controller to configure the local device as an RDM.