These topics describe VMware vSphere.

The following figure illustrates the basic components of VMware vSphere.

VMware vSphere Components
Architectural diagram, including clients, ESXi, vCenter Server, databases

Each vCenter Server system manages multiple ESX hosts. You can run the vSphere Client and vSphere Web Access on multiple workstations.

The major VMware vSphere components are:

VMware ESXi Embedded

Provides a virtualization layer that abstracts the processor, memory, storage, and networking resources of the physical host into multiple virtual machines. You do not need to install ESXi Embedded because it is embedded as firmware on hardware that you purchase from a vendor.

vCenter Server

A service that acts as a central administrator for ESX/ESXi hosts connected on a network. This service directs actions on the virtual machines and the hosts. The vCenter Server is the working core of vCenter. You can have multiple vCenter Server systems joined to a Linked Mode group. This allows you to log in to any single instance of vCenter Server and view and manage the inventories of all the vCenter Server systems in the group.

vCenter Server additional modules

Provide additional capabilities and features to vCenter Server. Generally, additional modules (sometimes called plug-ins) are released separately, install on top of vCenter Server, and can be upgraded independently. You can install additional modules on the same computer as the vCenter Server system or on a separate one. After the additional module is installed, you can activate the module’s client component, which enhances the vSphere Client with user interface (UI) options. Additional modules include vCenter Update Manager, vCenter Converter, and vCenter Guided Consolidation Service.

vSphere Client

Installs on a Windows machine and is the primary method of interaction with VMware vSphere. The vSphere Client acts as a console to operate virtual machines and as an administration interface into the vCenter Server systems and ESX hosts.

The vSphere Client is downloadable from the vCenter Server system and ESX hosts. The vSphere Client includes documentation for administrators and console users.


Organize all the configuration data for the VMware vSphere environment. For small deployments, the bundled Microsoft SQL Server 2005 Express database lets you set up to 5 hosts and 50 virtual machines. vCenter Server supports other database products for larger deployments. vCenter Update Manager also requires a database. VMware recommends that you use separate databases for vCenter Server and vCenter Update Manager.