The 42nd IPP Symposium
Doing What Works: Facebook's Innovation at Scale
Harry Li, Facebook
Every computer scientist appreciates a contribution that is fast, efficient, and elegant. If a design has these properties, we sometimes say that it is the right solution. In practice, finding the right solution is a dark art at best, and more often, a hole down which many of us purists fall. Building systems that work well enough for now and leaving room to re-evaluate later is the more pragmatic approach. In this talk, I will describe two innovations that have enabled Facebook to scale with a user base that grows exponentially. One innovation can be thought of as "the right way" and the other as "it works well enough." Both have been critical to Facebook's success.
In the first half, I will present Haystack, a novel data store optimized to serve billions of small (< 1MB) objects that are written once, read often, and deleted rarely. Haystack outperforms other storage solutions under Facebook's Photos workload. The key observation is that the main bottleneck at a scale of billions of small objects is accessing metadata. Haystack reduces the per object metadata size so that all of its metadata can fit in memory, eliding any disk operations for metadata.
In the second half, I will describe our cache/persistent storage architecture. To keep pace with 400+ million active users, Facebook aggressively uses memcache to reduce the load on MySQL databases. I will discuss the mechanisms we use to keep cached values consistent within a data center and across data centers while highlighting pain points of an architecture that has grown incrementally.
Harry Li is an engineer at Facebook. He is a part of the infrastructure group and works to ensure that Facebook's architecture continues to scale well. He received his Ph.D. in 2009 from the University of Texas at Austin where he focused on fault-tolerance, cooperative services, and mechanism design. Prior to working on distributed systems, Harry earned his Sc.B. in 2002 from Brown University. While he has lived in many places since his undergraduate days, the CIT will always be home on some level and he is happy to be returning.
