Optimizing Flash-based Key-value Cache Systems

Flash-based key-value cache systems, such as Facebook’s McDipper [1] and Twitter’s Fatcache [2], provide a cost-efficient solution for high-speed key-value caching. These cache solutions typically take commercial SSDs and adopt a Memcached-like scheme to store and manage key-value pairs in flash. Such a practice, though simple, is inefficient. We advocate to reconsider the hardware/software architecture design by directly opening device-level details to key-value cache systems. This co-design approach can effectively bridge the semantic gap and closely connect the two layers together. Leveraging the domain knowledge of key-value caches and the unique device-level properties, we can maximize the efficiency of a key-value cache system on flash devices while minimizing its weakness. We are implementing a prototype based on the Open-channel SSD hardware platform. Our preliminary experiments show very promising results.