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VMware vCenter Server Explained

 

 

VMware vcenter is a service that acts as a central administration point for VMware ESXi hosts connected on a network. This service directs actions on the virtual machines and the hosts. vCenter server software consists on many services and modules. The software is installed on a windows server. Vcenter server provides advanced features, such as VMware Distributed Resource Scheduler DRS, VMware High Availability, VMware Fault Tolerance, VMware vMotion, and VMware Storage vMotion. A single vcenter server instance supports a maximum of 1000 hosts. It also supports 10,000 virtual machines that are powered on at the same time. It supports 15000 registered virtual machines.

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. Linked mode groups are discussed in a later module.

The vCenter architecture relies on:

• VMware vsphere client: The same vsphere client used to manage ESXi hosts is used to connect to the vcenter server system. When an ESXi host is managed by vCenter server, administrators should always use vCenter Server to manage that host.
• vCenter Server database: the most critical components is that vcenter server database. The database stores the inventory items, security roles, resource pools, performance data, and other critical information for vCenter server.
• Active directory domain: Because the vCenter server is installed on a windows platform, security for the vcenter server system is built on window security. The vcenter system is not required to belong to an Active Directory domain. But if the vCenter server system is a member of an active directory domain, user accounts and groups from the domain will be available on the vcenter server system. If the vcenter system is not a member of a domain, then vcenter server uses local windows users and groups.
• Managed Hosts: vCenter server allows you to manage ESXi hosts as well as the virtual machines that run on them.

vCenter server consists of the following services and interfaces:

• Core services include management of resources and virtual machines, task scheduling, statistics logging, management of alarms and events, virtual machine provisioning, and host and virtual machine configuration.
• Distributed services include vMotion, DRS, and VMware HA. They are installed with vCenter server.
• Additional services are packaged separately from the base product and requires separate installation. No additional license is required. Examples include VMware vcenter update manager and vmware vcenter converter.
• Database interface provides access to the vcenter server database.
• ESXi management. Vcenter server provides access to the ESXi host through a vcenter server agent, which is installed on the host when it is added to the vcenter server inventory.
• The active directory interface provides access to domain accounts.
• The vmware vsphere API, in combination with vsphere SDK, provide an API for writing custom applications that access vcenter server.
  
  

 

vCenter server modules are applications that provide additional features.

Typically, modules include a server component and a client component. After the server component of a module is installed, it is registered with vCenter server and the client component is available to vsphere client for download. After a plug-in is installed on a vsphere client, it might alter the interface by adding view, tabs, toolbar buttons, and menu options related to the enhanced functionality.

Additional vCenter server modules:

• Update manager—works with ESXi hosts, virtual machines and virtual appliances running on ESXi hosts. Update Manager allows you to scan for compliance and apply updates for guest operating systems, virtual appliances, and hosts.
• vCenter converter – enables users to convert physical machines and virtual machines in a variety of formats, to virtual machines that run on ESXi hosts. Converted systems can be imported into any location in the vCenter server inventory.

These modules use core vCenter server capabilities, such as authentication and permission management, but can have their own types of events, tasks, metadata, and privileges. Modules require vcenter server. They can installed any time after vCenter server has been installed. Modules and vcenter server can be upgraded independently.

 

vCenter server, Physical or Virtual
vCenter server can run on a physical machine or a virtual machine. When vCenter Server is run on a physical machine, a dedicated server is required. But vCenter server is not susceptible to potential outage in the vSphere environment. Backup of vCenter server files are done with traditional backup tools. Vcenter performance is limited by the capacities of the server hardware.

Advantages to running vCenter server in a virtual machine:

• Instead of dedicated an entire physical server to vCenter server, you can run it in a virtual machine on the same ESXi hosts as other virtual machines. But it is better to place the vCenter server virtual machine outside the environment that you are managing.
• By encapsulating the vCenter server instance in a virtual machine, you can transfer it from one host to another, easing maintenance and other activities.
• With VMware HA, you can provide high availability for vCenter server system.