Speaker: Jeff Terrace, Princeton University
Title: Object Storage on CRAQ: High-throughput chain replication 
       for read-mostly workload 

Abstract:

Massive storage systems typically replicate and partition data over
many potentially-faulty components to provide both reliability and
scalability. Yet many commercially-deployed systems, especially those
designed for interactive use by customers, sacrifice stronger
consistency properties in the desire for greater availability and
higher throughput.  This paper describes the design, implementation,
and evaluation of CRAQ, a distributed object-storage system that
challenges this inflexible tradeoff. Our basic approach, an
improvement on Chain Replication, maintains strong consistency while
greatly improving read throughput. By distributing load across all
object replicas, CRAQ scales linearly with chain size without
increasing consistency coordination. At the same time, it exposes
non-committed operations for weaker consistency guarantees when this
suffices for some applications, which is especially useful under
periods of high system churn. This paper explores additional design
and implementation considerations for geo-replicated CRAQ storage
across multiple datacenters to provide locality-optimized operations.
We also discuss multi-object atomic updates and multicast
optimizations for large-object updates.