6.5.1

Because virtual machines are decoupled from specic underlying physical hardware, virtualization allows
you to consolidate physical computing resources such as CPUs, memory, storage, and networking into pools
of resources. These resources can be dynamically and exibly made available to virtual machines. With
appropriate management software, such as vCenter Server, you can also use several features that increase
the availability and security of your virtual infrastructure.
Physical Topology of vSphere Data Center
A typical VMware vSphere data center consists of basic physical building blocks such as x86 virtualization
servers, storage networks and arrays, IP networks, a management server, and desktop clients.
The vSphere data center topology includes the following components.
Compute servers
Industry standard x86 servers that run ESXi on the bare metal. ESXi software
provides resources for and runs the virtual machines. Each computing server
is called a standalone host in the virtual environment. You can group a
number of similarly congured x86 servers with connections to the same
network and storage subsystems. This grouping creates an aggregate set of
resources in the virtual environment, called a cluster.
Storage networks and
arrays
Fibre Channel SAN arrays, iSCSI SAN arrays, and NAS arrays are widely
used storage technologies supported by VMware vSphere to meet dierent
data center storage needs. The storage arrays are connected to and shared
between groups of servers through storage area networks. This arrangement
allows aggregation of the storage resources and provides more exibility in
provisioning them to virtual machines.
IP networks
Each compute server can have multiple physical network adapters to
provide high bandwidth and reliable networking to the entire VMware
vSphere data center.
vCenter Server
vCenter Server provides a single point of control to the data center. It
provides essential data center services such as access control, performance
monitoring, and conguration. It unies the resources from the individual
computing servers to be shared among virtual machines in the entire data
center. It manages the assignment of virtual machines to the computing
servers and the assignment of resources to the virtual machines within a
given computing server. These assignments are based on the policies that the
system administrator sets.
Computing servers continue to function even in the unlikely event that
vCenter Server becomes unreachable (for example, if the network is severed).
Servers can be managed separately and continue to run the virtual machines
assigned to them based on the resource assignment that was last set. After
connection to vCenter Server is restored, it can manage the data center as a
whole again.
Management clients
VMware vSphere provides several interfaces for data center management
and virtual machine access. These interfaces include vSphere Web Client for
access through a web browser or vSphere Command-Line Interface (vSphere
CLI).
vCenter Server and Host Management
14 VMware, Inc.