The Synchronous Data Center

Today, distributed systems are typically designed to be largely asynchronous. Designers assume that the network can drop or significantly delay messages at unpredictable times, that there is no way to know how quickly a node might process a message, or how soon it might respond, and that the clocks of different nodes are at most loosely synchronized. These assumptions are certainly safe, but they come at a price: many applications really do need predictable performance, which, on top of an asynchronous system, has to be approximated at great cost and with lots of redundancy, and many distributed protocols for asynchronous systems are much more complex and expensive than their synchronous counterparts. The goal of this paper is to start a discussion about whether the asynchronous model is (still) the right choice for most distributed systems, especially ones that belong to a single administrative domain. We argue that 1) by using ideas from the CPS domain, it is technically feasible to build datacenter-scale systems that are fully synchronous, and that 2) such systems would have several interesting advantages over current designs.