Gemini: A Distributed Crash Recovery Protocol for Persistent Caches

Gemini is a distributed crash recovery protocol for persistent caches. When a cache instance fails, Gemini assigns other cache instances to process its reads and writes. Once the failed instance recovers, Gemini starts to recover its persistent content while using it to process reads and writes immediately. Gemini does so while guaranteeing read-after-write consistency. It also transfers the working set of the application to the recovering instance to maximize its cache hit ratio. Our evaluation shows that Gemini restores hit ratio two orders of magnitude faster than a volatile cache. Working set transfer is particularly effective with workloads that exhibit an evolving access pattern.