Amy Tai will present her PreFPO on Wednesday, June 6, 2018 at 1:00 pm in CS 402. Committee: Mike Freedman (advisor) Jen Rexford Kai Li Kyle Jamieson Wyatt Lloyd All are welcomed to attend. Title: Leveraging Distributed Storage Redundancy in Datacenters Abstract: Replication is a widely used primitive in distributed storage systems to achieve properties such as durability and availability. In this talk, I will discuss two projects in which we design and implement two novel properties that replication can achieve. With each property, we also define the set of tradeoffs introduced as well as propose new techniques for exploring these tradeoffs. Our work shows that replication has several more useful properties than previously assumed. First, I will discuss Replex, which harnesses distributed storage redundancy to build distributed secondary indices. Traditionally, storage systems punt on building fully functional distributed secondary indices because they do not have the correct primitive for doing so. We introduce a new replication primitive, a replex, that treats distributed secondary indices as first-class data objects. The tradeoff that results is between steady-state and failure performance, and we explore this tradeoff with a primitive we denote a hybrid replex. Second, I will discuss DIRECT, which is a set of principles for systematically leveraging storage redundancy to fix corruption errors in live production storage systems. Corruption errors are generally treated as device failures in today's storage systems, but we show that by fixing them online, we can extend the lifetime of flash devices by orders of magnitude. The tradeoff that results is between size of failure domain (and hence time to recovery) and ease of implementation. Barbara A. Mooring Interim Graduate Coordinator Computer Science Department Princeton University