Thanks. I'd like the underlying guest to access the physical drive (it's a NAS, I don't want a layer of virtualizaion between it and the HDDs).
I thought this would be a cakewalk, with the maturity of ESXi and all...
The 4TB drives are connected to the local SATA ports (on board), which, I understand, makes life more difficult.
I seem to gather, from all I read, that it's not possible for large drives, neither via RDM nor via a raw device VMDK. I guess I just need an authoritative answer :-)