Introduction to Virtualization - Oracle Solaris 10 System Virtualization Essentials - page 2

is called operating system virtualization (OSV). In this model, each environment
contains what appears to be a private copy of the operating system in a container
(a similar technology calls them jails ). This approach is different than the second
model, in which multiple operating system instances run on one set of hardware
resources. The latter model takes advantage of virtual machines (VMs), which
may run the same or different operating systems. Virtual machines are provided
by hardware and/or software called a hypervisor , which creates the illusion of
a private machine for each “guest” OS instance. In the third model, hardware
partitioning ensures the electrical segregation of computer hardware resources—
CPUs, RAM, and I/O components—so as to create multiple independent comput-
ers within one computer. Each isolated grouping of hardware is called a partition
or domain .
Through the course of the topic, we will describe different forms of computer
virtualization in detail. The phrase “virtual environment” (VE) will be used to
refer to any of these types of virtualization.

1.1.2 Why Virtualize?
The original and most common reason to virtualize is to facilitate server con-
solidation, although several other important purposes exist as well. Today's data
center managers face a series of extreme challenges: They must continue to add
to compute workloads while minimizing operational costs, which include the elec-
tricity to power and cool computing systems. In data centers that are already full,
this requirement necessitates squeezing existing workloads into unused compute
capacity on existing systems and increasing the workload density of new systems.
New servers are better able to handle this task than older ones. For example,
you can move workloads on older Sun Fire V880 systems running Solaris 8 to
Sun SPARC Enterprise T5240 computers running Oracle Solaris 10 with minimal
effort. Because of the performance characteristics of the two types of systems, for
most workloads six V880s can be replaced by one T5240.
Replacing 100 V880 computers with 17 T5240s would achieve the following
improvements:

Aggregate throughput performance would not change significantly for most
workloads.

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Reduced space: 100 V880s use 50 data center racks, whereas 17 T5240s can
fit in a single data center rack.

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Approximately 660,000 BTUs of heat generation would be removed from the
data center.

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