Methods, systems, and computer program products for high-performance cluster computing. Multiple components are operatively interconnected to carry out operations for high-performance RDMA I/O transfers over an RDMA NIC. A virtual machine of a virtualization environment initiates a first I/O call to an HCI storage pool controller using RDMA. Responsive to the first I/O call, a second I/O call is initiated from the HCI storage pool controller to a storage device of an HCI storage pool. The first I/O call to the HCI storage pool controller is implemented through a first virtual function of an RDMA NIC that is exposed in the user space of the virtualization environment. Prior to the first RDMA I/O call, a contiguous unit of memory to use in an RDMA I/O transfer is registered with the RDMA NIC. The contiguous unit of memory comprises memory that is registered using non-RDMA paths such as TCP or iSCSI.