The reduced costs and increased power of commodity hardware are not the only contributors to the explosion of cloud computing. The availability of increasingly sophisticated software tools has also had an impact. Perhaps the most important software tool in the cloud computing toolbox is virtualizationvirtualizationA type of software that allows a single computer (or cluster of connected computers) to function as if it were several different computers, each running its own operating system and software. Virtualization software underpins most cloud computing efforts, and can make computing more efficient, cost effective, and scalable.. Think of virtualization as being a kind of operating system for operating systems. A server running virtualization software can create smaller compartments in memory that each behave as a separate computer with its own operating system and resources. The most sophisticated of these tools also allow firms to combine servers into a huge pool of computing resources that can be allocated as needed.^[457]

Virtualization can generate huge savings. Some studies have shown that on average, conventional data centers run at 15 percent or less of their maximum capacity. Data centers using virtualization software have increased utilization to 80 percent or more.^[458] This increased efficiency means cost savings in hardware, staff, and real estate. Plus it reduces a firm’s IT-based energy consumption, cutting costs, lowering its carbon footprint, and boosting “green cred.”^[459] Using virtualization, firms can buy and maintain fewer servers, each running at a greater capacity. It can also power down servers until demand increases require them to come online.

While virtualization is a key software building block that makes public cloud computing happen, it can also be used in-house to reduce an organization’s hardware needs, and even to create a firm’s own private cloud of scalable assets. Bechtel, BT, Merrill Lynch, and Morgan Stanley are among the firms with large private clouds enabled by virtualization.^[460] Another kind of virtualization, virtual desktopsvirtual desktopWhen a firm runs an instance of a PC’s software on another machine and simply delivers the image of what’s executing to the remote device. Using virtualization, a single server can run dozens of PCs, simplifying backup, upgrade, security, and administration. allow a server to run what amounts to a copy of a PC—OS, applications, and all—and simply deliver an image of what’s executing to a PC or other connected device. This allows firms to scale, back up, secure, and upgrade systems far easier than if they had to maintain each individual PC. One game start-up hopes to remove the high-powered game console hardware attached to your television and instead put the console “in the cloud,” delivering games to your TV as they execute remotely on superfast server hardware. Virtualization can even live on your desktop. Anyone who’s ever run Windows in a window on Mac OS X is using virtualization software; these tools inhabit a chunk of your Mac’s memory for running Windows and actually fool this foreign OS into thinking that it’s on a PC.

Interest in virtualization has exploded in recent years. VMware, the virtualization software division of storage firm EMC, was the biggest IPO of 2007. But its niche is getting crowded. Microsoft has entered the market, building virtualization into its server offerings. Dell bought a virtualization software firm for $1.54 billion. And there’s even an open source virtualization product called Xen.^[461]