Modern storage systems are required to scale to large storage capacities and I/O throughput in a cost effective manner. For this reason, they are increasingly being built out of commodity components, mainly PCs equipped with large numbers of disks and interconnected of high-performance system area networks. A main issue in these efforts is to achieve high I/O throughput over commodity, low-cost system area networks and commodity operating systems. In this work, we examine in detail the performance of remote block-level storage I/O over commodity, RDMA-capable network interfaces and networks. We examine the support that is required from the network interface for achieving high throughput. We also examine in detail the overheads associated in kernel-level protocols for networked storage access. We find that base system performance is limited by (a) interrupt cost, (b) request size, and (c) protocol message size. We examine the impact of techniques to alleviate these factors and find that our techniques combined can improve throughput by up to 100 % over a simpler unoptimized configuration. Our current prototype is able to achieve a throughput of about 200 MBytes/s over a network that is capable of delivering about 500 MBytes/s. We identify major limiting factors, mostly at the I/O target-side.

State-of-the-art high-speed network intrusion detection and prevention systems are often designed using multiple intrusion detection sensors operating in parallel coupled with a suitable front-end load-balancing traffic splitter. In this paper, we argue that, rather than just passively providing generic load distribution, traffic splitters should implement more active operations on the traffic stream, with the goal of reducing the load on the sensors. We present an active splitter architecture and three methods for improving performance. The first is early filtering/forwarding, where a fraction of the packets is processed on the splitter instead of the sensors. The second is the use of locality buffering, where the splitter reorders packets in a way that improves memory access locality on the sensors. The third is the use of cumulative acknowledgments, a method that optimizes the coordination between the traffic splitter and the sensors. Our experiments suggest that early filtering reduces the number of packets to be processed by 32 percent, giving an 8 percent increase in sensor performance, locality buffers improve sensor performance by 10-18 percent, while cumulative acknowledgments improve performance by 50-90 percent. We have also developed a prototype active splitter on an IXP1200 network processor and show that the cost of the proposed approach is reasonable.