I'd lean to using a physical RDM as well, but keep in mind that RDMs are not officially supported on local storage -
- kb.vmware.com/kb/1017704
- kb.vmware.com/kb/1017530
You can work around that by using the console or vCLI to create the RDM.
If the 20 TB of storage won't be used for anything else and you have additional storage in the host you could consider using VMDirectpath to pass through the RAID controller into the VM.