DAX: A Widely Distributed Multitenant Storage Service for DBMS Hosting
Many applications hosted on the cloud have sophisticated data management needs that are best served by a SQL-based relational DBMS. It is not difficult to run a DBMS in the cloud, and in many cases one DBMS instance is enough to support an application's workload. However, a DBMS running in the cloud (or even on a local server) still needs a way to persistently store its data and protect it against failures. One way to achieve this is to provide a scalable and reliable storage service that the DBMS can access over a network. This paper describes such a service, which the authors call DAX. DAX relies on multi-master replication and Dynamo-style flexible consistency, which enables it to run in multiple data centers and hence be disaster tolerant.