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common to related solutions in the industry. Implementations specific to the
Oracle Solaris ecosystem are described in Chapters 2 through 6.
Each of the descriptions in this chapter mentions that model's traits and
strengths. A detailed analysis of their relative strengths and weaknesses is pro-
vided in Chapter 7, “Choosing a Virtualization Technology.”
The epitome of isolation within the same computer comprises complete separation
of compute resources—software and hardware—while still achieving some level of
savings or flexibility compared to separate systems. In the ideal case, an electri-
cally isolated environment (a partition) is an independent system resource that
runs its own copy of an operating system. The OS runs directly on the hardware,
just as in a completely non-virtualized environment. Any single failure, whether
in hardware or software, in a component of one VE cannot affect another VE in
the same physical computer. Hard partitions are used, for example, to consolidate
servers from different company departments where isolation and technical sup-
port chargebacks are required.
In some implementations, the only shared component is the system cabinet,
although such an approach yields little cost savings. This is especially true if the
resources in different partitions cannot be merged into larger VEs. Other imple-
mentations share interconnects, clock control, and, in some cases, multiple hard
partitions on a single system board. On a practical level, the minimum components
held in common would consist of the system cabinet, redundant power supplies
and power bus and, to promote flexible configurations and minimally qualify as
virtualization, a shared but redundant backplane or interconnect. The label “vir-
tualization” can be applied to these systems because the CPUs, memory, and I/O
components can be reconfigured on the fly to any partition while still maintaining
fault isolation. This limited set of common components provides the best failure
isolation possible without using separate computers.
Because of the characteristics of hard partitioning, some people do not con-
sider partitioning to qualify as virtualization. Because of the role that hardware
partitioning plays in consolidating and isolating workload environments, we will
include this model in our discussions.
The next few sections discuss some of the relevant factors of hardware isolation.
1.2.1.1 Failure Isolation
Limiting the set of components that are common to two different partitions in-
creases the failure isolation of those environments. With this approach, a failure
of any hardware component in one partition will not affect another partition in
the same system. Any component that can be shared, such as the backplane, must
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