Performance of RDMA-capable storage protocols on wide-area network

Because of its high throughput, low CPU utilization, and direct data placement, RDMA (Remote Direct Memory Access) has been adopted for transport in a number of storage protocols, such as NFS and iSCSI. In this presentation, we provide a performance evaluation of RDMA-based NFS and iSCSI on Wide-Area Network (WAN). We show that these protocols, though benefit from RDMA on Local Area Network (LAN) and on WAN of short distance, are faced with a number of challenges to achieve good performance on long distance WAN. This is because of (a) the low performance of RDMA reads on WAN, (b) the small 4 KB chunks used in NFS over RDMA, and(c)the lack of RDMA capability in handling discontinuous data. Our experimental results document the performance behavior of these RDMA-based storage protocols on WAN.