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grows to consume the maximum quantity of a particular resource, you must pur-
chase a larger system and move the workload to it. Without virtualization, this
type of upgrade typically means installing the operating system and applications
on the new computer, which is a time-consuming and error-prone process.
With virtualization, fewer larger systems can be deployed, reducing the com-
plexity of managing many systems. When a workload outgrows its system, an
existing system with sufficient unused capacity can usually be found. Using the
various tools available to migrate a VE from one system to another, this process
can be as simple as clicking and dragging an icon in a management application.
Figure 1.14 shows a migration to a larger system, where the application will rarely
be constrained by the quantity of resources in the computer.
Figure 1.14
Providing More Room for a VE
1.1.6.9 Fine-Grained Operating System Modification
A challenge of consolidated but non-virtualized workloads is the decreased flex-
ibility of the system. One workload may need a particular version of an operating
system or a specific set of tuning parameters for the operating system. One ap-
plication may be tested and supported only with a specific set of operating system
components installed. Without virtualization, it is sometimes difficult to meet the
needs of every workload on a consolidated system.
System virtualization technologies virtualize an instance of an operating sys-
tem or of a computer. In each case, one VE can be tailored to meet the needs of its
workload, while another VE is customized to meet the needs of another workload.
1.1.6.10 Configurable Security Characteristics
Single-user systems have security needs, such as firewall features to keep out
intruders. Multiuser systems have all of these needs plus some unique ones of
their own—for example, mechanisms to protect one user from another. Systems
with VEs also have their own specific security considerations.
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