Cloud Computing

CHAPTER 6 Cloud Storage and the Structure of a Modern Data Center

Data centers are the workhorses of Cloud Computing.

A data center is where servers, storage, and communication gear reside along with the necessary utilities (e.g., power, cooling, and ventilation equipment). Co-locating equipment this way is natural, since the environmental needs and physical security needs are often common. It also simplifies operations and maintenance. A case in point is that ten computers in a single room are easier to safeguard physically than when the same ten computers are distributed across five rooms.

Most data centers consume vast amounts of energy unnecessarily, wasting 90% or more of the electricity they draw from the grid [1].¹ One reason² for such inefficiency is under-utilization of servers: typical utilization figures range from 6% to 12%. Virtualization of data centers offers a way to increase server utilization and reduce energy consumption. It also sets loose the traditional delineation of data centers by hardware, physical casing and wiring, floor space, and other physical attributes.

The resulting virtual data centers no longer have well-defined physical boundaries. It goes without saying that a physical data center may host multiple virtual data centers. If the virtual data centers are intended for more than one organization, the physical data center is multi-tenant.

But it is also possible to have a virtual data center spanning multiple physical data centers. For instance, ...