Virtualizing Resources for the Cloud

Virtualization is at the core of cloud computing. It lies on top of the cloud infrastructure, whereby virtual resources (e.g., virtual CPUs, memories, disks and networks) are constructed from the underlying physical resources and act as proxies to them. As is the case with the idea of cloud computing, which was first introduced in the 1960s [1], virtualization can be traced back to the 1970s [55]. Forty years ago, the mainframe computer systems were extremely large and expensive. To address expanding user needs and costly machine ownerships, the IBM 370 architecture, announced in 1970, offered complete virtual machines (virtual hardware images) to different programs running at the same computer hardware. Over time, computer hardware became less expensive and users started migrating to low-priced desktop machines. This drove the adoption of the virtualization technology to fade for a while. Today, virtualization is enjoying a resurgence in popularity with a number of research projects and commercial systems providing virtualization solutions for commodity PCs, servers, and the cloud. In this chapter, we present various ingredients of the virtualization technology and the crucial role it plays in enabling the cloud computing paradigm. First, we identify major reasons for why virtualization is becoming important, especially for the cloud. Second, we indicate how multiple software images can run side-by-side on physical resources while attaining security, resource and failure isolations. Prior to delving into more details about virtualization, we present a brief background requisite for understanding how physical resources can be virtualized. In particular,