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The Greening of IT
96 How Companies Can Make a Difference for the Environment

The benefits of client virtualization are many, and not only to the energy
balance. Software deployment in an office environment, for example, can
become difficult if each desktop machine contains many different types and
versions of software. Client virtualization where the clients all run applica-
tions on a central server solves the software problem.
As we’ve discussed, a thin client is a computer (client) in client-server
architecture networks, which depends primarily on the central server for pro-
cessing activities. In contrast, a thick or fat client does as much processing as
possible and passes only data required for communications and archival stor-
age to the server. A thin client is often a network computer without a hard
disk drive. Here are some benefits and risks:

■ Benefits: The significant benefits of client virtualization and the use of
thin clients are the low cost of ownership (including lower energy use),
security, and reliability. Boot image control is much simpler when only
thin clients are used—typically a single boot image can accommodate a
very wide range of user needs, and be managed centrally. Thin client
technology can be a significant benefit—for example, to support help
ptg
desks where everyone at the help desk needs to access the same server
applications.
■ Risks: The major risks to moving to thin client technology include the
loss of flexibility when moving from a thick client. Our laptops are thick
clients and give us the flexibility to use them anywhere, with or without
a network connection. Also, a server that supports thin clients must have
a higher level of performance since it does all of the processing for the
thin clients. Thick clients also have advantages in multimedia-rich appli-
cations that would be bandwidth intensive if fully served. But the major
risk moving to thin clients is loss of flexibility. On some operating sys-
tems (such as Microsoft Windows), software products are designed for
personal computers that have their own local resources. Trying to run this
software in a thin client environment can be difficult.

In general, virtualization, including client virtualization, will signifi-
cantly reduce total cost of ownership (TCO) and energy consumption. In the
case of a desktop PC, Gartner projects that if IT were to virtualize the graph-
ical user interface of all PC applications and manage the software centrally,
indirect IT costs would be cut in half. For IT, that represents a considerable
amount of savings, as cutting indirect costs in half cuts PC TCO by about
one third.