Virtualization Management - Oracle Solaris 10 System Virtualization Essentials - page 311

a VE, and many of today's virtualization tools allow this property to be modi-
fied. A workload that outgrows the physical constraints of a computer needs a
larger computer. Although you could re-implement that workload and its software
infrastructure on a different system, that choice would require considerable in-
vestment of effort, would probably include many manual steps that provide op-
portunities for human error, and would require a service outage. New virtualiza-
tion tools enable you to move the VE to the larger computer with a small service
outage—perhaps one short enough that no one would notice. In addition, a very
small number of steps are used in this migration process, thereby minimizing the
chances for human error.
The economics of the computer industry limit the RAS (reliability, availability,
and serviceability) characteristics available on smaller systems. Such low-end sys-
tems tend to run small, less important workloads, which do not justify the expense
of redundant, hot-swappable components that are not necessary for computation.
For example, a server that is sold for $1000 will not include a second redundant
$100 power supply.
By comparison, larger, more expensive systems are needed for large business-
critical workloads. The business value of these workloads justifies the additional
component cost of redundant power supplies. These enhanced RAS features im-
prove the computer's ability to run after suffering a hardware failure—for ex-
ample, a failed power supply. The value of this type of workload often justifies
the additional cost. Multiple CPUs, memory DIMMs, and I/O controllers can also
be redundant in this setting. In addition to the value that enhanced RAS offers
a single critical workload, these features are more important for a server that
will house multiple workloads because more people and business processes are
affected by a hardware outage.
Every physical computer has its own properties, so moving a VE from one com-
puter to another can modify many properties at once. Besides increasing physical
resources such as CPUs and memory, the VE's new home might also have better
RAS characteristics. A workload that was originally unimportant might have been
implemented on a small computer with minimal RAS. Over time, that workload
might have evolved to become very important, justifying its placement on a more
expensive computer with multiple redundant components.
Virtualization, when properly managed, can improve the operational flexibility
of a business, providing tools to deal with both expected and unexpected changes
in business needs.
9.2.2.2 Business Agility
Business agility is the ability of a business to adapt to changing conditions. In
the context of a data center, this concept focuses on the ability to nondisruptively
match changing business needs with workloads and changing workload capacity.