Scaling Out to a Single-Node 80Gbps Memcached Server with 40Terabytes of Memory.

Current web infrastructure relies increasingly on distributed in-memory key-value stores such as memcached whereby typical x86-based implementations of TCP/IP compliant memcached yield limited performance scalability. FPGA-based data-flow architectures overcome and exceed every other published and fully compliant implementation in regards to throughput and provide scalability to 80Gbps, while offering much higher power efficiency and lower latency. However, value store capacity remains limited given the DRAM support in today's devices. In this paper, we present and quantify novel hybrid memory systems that combine conventional DRAMs and serial-attached flash to increase value store capacity to 40Terabytes with up to 200 million entries while providing access at 80Gbps. This is achieved by an object distribution based on size using different storage devices over DRAM and flash and data-flow based architectures using customized memory controllers that compensate for large variations in access latencies and bandwidths. We present measured experimental proofpoints, mathematically validate these concepts for published value size distributions from Facebook, Wikipedia, Twitter and Flickr and compare to existing solutions.