Multitenant data infrastructures for large cloud platforms hosting hundreds of thousands of applications face the challenge of serving applications characterized by small data footprint and unpredictable load patterns. When such a platform is built on an elastic pay-per-use infrastructure, an added challenge is to minimize the system’s operating cost while guaranteeing the tenants ’ service level agreements (SLA). Elastic load balancing is therefore an important feature to enable scale-up during high load while scaling down when the load is low. Live migration, a technique to migrate tenants with minimal service interruption and no downtime, is critical to allow lightweight elastic scaling. We focus on the problem of live migration in the database layer. We propose Zephyr, a technique to efficiently migrate a live database in a shared nothing transactional database architecture. Zephyr uses phases of ondemand pull and asynchronous push of data, requires minimal synchronization, results no service unavailability and few or no aborted transactions, minimizes the data transfer overhead, provides ACID guarantees during migration, and ensures correctness in the presence of failures. We outline a prototype implementation using an open source relational database engine and an present a thorough evaluation using various transactional workloads. Zephyr’s efficiency is evident from the few tens of failed operations, 10-20% change in average transaction latency, minimal messaging, and no overhead during normal operation when migrating a live database. Categories and Subject Descriptors H.2.4 [Database Management]: Systems—Relational databases,

Scalable database management systems (DBMS)—both for update intensive application workloads as well as decision support systems for descriptive and deep analytics—are a critical part of the cloud infrastructure and play an important role in ensuring the smooth transition of applications from the traditional enterprise infrastructures to next generation cloud infrastructures. Though scalable data management has been a vision for more than three decades and much research has focussed on large scale data management in traditional enterprise setting, cloud computing brings its own set of novel challenges that must be addressed to ensure the success of data management solutions in the cloud environment. This tutorial presents an organized picture of the challenges faced by application developers and DBMS designers in developing and deploying internet scale applications. Our background study encompasses both classes of systems: (i) for supporting update heavy applications, and (ii) for ad-hoc analytics and decision support. We then focus on providing an in-depth analysis of systems for supporting update intensive web-applications and provide a survey of the state-of-theart in this domain. We crystallize the design choices made by some successful systems large scale database management systems, analyze the application demands and access patterns, and enumerate the desiderata for a cloud-bound DBMS.

Abstract. Cloud computing has emerged as an extremely successful paradigm for deploying web applications. Scalability, elasticity, pay-per-use pricing, and economies of scale from large scale operations are the major reasons for the successful and widespread adoption of cloud infrastructures. Since a majority of cloud applications are data driven, database management systems (DBMSs) powering these applications form a critical component in the cloud software stack. In this article, we present an overview of our work on instilling these above mentioned “cloud features ” in a database system designed to support a variety of applications deployed in the cloud: designing scalable database management architectures using the concepts of data fission and data fusion, enabling lightweight elasticity using low cost live database migration, and designing intelligent and autonomic controllers for system management without human intervention.

The current model of the cloud consists of a static set of data centers (or cloud cores) which drive the computation and storage needs of large numbers of applications. We envision a new paradigm where the cloud will be comprised of a large dynamic collection of cloud cores along with a static set of cores, the nucleus, to create a cloud computing universe with a capacity much larger than the nucleus and a cost much smaller than owning the entire infrastructure. This model is rooted by the observation that a tremendous amount of computation exists outside the core that can potentially augment the nucleus ’ capacity. An example of this surplus capacity are enterprizes with diurnal trends in usage behavior that join the cloud during predicted periods of usage troughs. We propose to leverage this elastic and dynamic infrastructure to create a unified cloud service. A number of challenges, at all levels of the software stack, need to be addressed for these futuristic architectures to become a reality. We focus on the challenge of an elastic and agile data management infrastructure to deal with the dynamics associated with this novel paradigm.