Specifications

vCenter Server is a single Windows Service and is installed to run
automatically. vCenter Server runs continuously in the background. It
performs its monitoring and managing activities even when no vSphere Clients
are connected and when no one is logged on to the computer where it resides.
It must have network access to all the hosts it manages and be available for
network access from any machine where the vSphere Client is run.
You can install vCenter Server in a Windows virtual machine on an ESXi host,
allowing it to take advantage of the high-availability that is provided by
VMware HA. See the vSphere Installation and Setup documentation for details
about setting up this configuration.
You can join multiple vCenter Server systems using Linked Mode to allow them
to be managed using a single vSphere Client connection.
vCenter Server plug-ins
Applications that provide additional features and functionality to
vCenter Server. Typically, plug-ins consist of a server component and a client
component. After the plug-in server is installed, it is registered with
vCenter Server and the plug-in client is available to vSphere clients for
download. After a plug-in is installed on a vSphere client, it might alter the
interface by adding views, tabs, toolbar buttons, or menu options related to the
added functionality.
Plug-ins leverage core vCenter Server capabilities, such as authentication and
permission management, but can have their own types of events, tasks,
metadata, and privileges.
Some vCenter Server features are implemented as plug-ins, and can be
managed using the vSphere Client Plug-in Manager. These features include
vCenter Storage Monitoring, vCenter Hardware Status, and vCenter Service
Status.
vCenter Server database
A persistent storage area for maintaining the status of each virtual machine,
host, and user managed in the vCenter Serverenvironment. The
vCenter Server database can be remote or local to the vCenter Server system.
The database is installed and configured during vCenter Server installation.
If you are accessing your ESXi host directly through a vSphere Client, and not
through a vCenter Server system and associated vSphere Client, you do not
use a vCenter Server database.
Tomcat Web server
Many vCenter Server functions are implemented as Web services that require
the Tomcat Web server. The Tomcat Web server is installed on the vCenter
Server machine as part of the vCenter Server installation.
Features that require the Tomcat Web server to be running include: Linked
Mode, CIM/Hardware Status tab, Performance charts, WebAccess, vCenter
Storage Monitoring/Storage Views tab, and vCenter Service status.
vCenter Server agent
On each managed host, the software that collects, communicates, and executes
the actions received from vCenter Server. The vCenter Server agent is installed
the first time any host is added to the vCenter Server inventory.
vCenter Server and Host Management
14 VMware, Inc.