Chapter 2. VMware vCenter Server

In the last chapter, we discussed about various hypervisors and VMware vSphere. We understood how vSphere differs from other products, and how a virtual environment is a better choice in managing a data center. We now also know what our virtual infrastructure comprises of. So after having an introductory understanding of VMware vSphere, we will now have a look at vCenter Server and its role in VMware virtualized infrastructure.

We will cover the following topics in this chapter:

Introduction to vCenter Server
vCenter Server architecture
Communication between vCenter Server and ESXi hosts
Additional vCenter Server components
Comparison of vCenter Server and vCenter Server Appliance
Preparing and installing vCenter Server on Microsoft Windows
Importing, starting and configuring the vCenter Server Appliance
Configuring and managing vCenter Server
Managing inventory, hosts, VMs, and templates via vCenter Server
vCenter Server licensing
Backing up vCenter Server...

Introduction to vCenter Server

To start with, vCenter Server is the centralized management utility by VMware, and is used to manage virtual machines, multiple ESXi hosts, and all dependent components from a single centralized location. Using this tool, you're also able to take full control of advanced components including distributed switches, vMotion, Storage vMotion, templates, and clones.

vCenter Server architecture

In order to understand how vCenter Server works, it is important to understand its architecture.

The vCenter Server architecture is made up of the following components:

vSphere Web Client and vSphere Client: As discussed in the previous chapter, VMware offers both vSphere Web Client and vSphere legacy client to manage ESXi hosts and virtual machines. The vSphere legacy client can be used to connect directly to an ESXi host or to vCenter Server, but vSphere Web Client is used to connect only to the vCenter Server, not individual ESXi hosts.
- The recommendation from VMware is to use VMware vCenter Server to manage ESXi hosts and virtual machines, and therefore use vSphere Web Client, as all the new features are available only through the use of vSphere Web Client. New customers should start with vSphere Web Client in any case, as VMware plans to give up the legacy client some day.
vCenter Server database: It is the most crucial component of the architecture. It stores...

Communication between vCenter Server and ESXi hosts

The main service running on the vCenter Server is known as vpxd or VMware Virtual Server service. When an ESXi host is added to the vCenter Server, there is an agent service called vpxa, which is installed and started on the ESXi host. Vpxa acts as an intermediary service between the vpxd service running on the vCenter Server and hostd service running on the ESXi host. The hostd service running on the ESXi host is mainly responsible for managing most of the operations on the host.

It knows all the registered virtual machines, their status, and the storage volumes that are visible to the host. When commands such as creating, migrating, or suspending a virtual machine from vCenter Server is issued, the vpxd service running on the vCenter Server sends the command to vpxa, and vpxa in turn forwards it to hostd, which then executes the command.

If a command is issued through the vCenter Server, the vCenter Server database is also updated. vCenter...

Additional vCenter Server components

vCenter Server also consists of the following services and interfaces:

Core services: This includes managing resources and virtual machines, scheduling tasks, managing and generating events and alarms, and logging statistics. It also offers functionality for provisioning virtual machines and configuring hosts.
Distributed services: This offers functionality for serving vSphere clusters, including (storage) vMotion, (storage) DRS, and high availability. While vMotion and storage vMotion are used for migrating virtual machines and their virtual hard disks online, DRS and Storage DRS implement automatic load balancing of computing and storage resources. vSphere high availability makes sure that virtual machines are restarted as fast as possible when an ESXi host crash happens.
Additional services: vCenter Server can be integrated with additional VMware products, including vSphere Update Manager (vUM) or vCenter Orchestrator. Some additional components like...

Comparison of vCenter Server and vCenter Server Appliance

In order to manage your virtualized data center, you are provided with some alternatives to install vCenter Server:

Installation on a supported Windows-based operating system
Deployment as a Linux-based virtual appliance (vCSA)

Both variants are quite similar as they both offer a wide range of management functionality, including:

Deployment and management of virtual machines, templates, and OVF appliances
Management of multiple ESXi hosts
Centralized network and storage provisioning
Statistics and performance data collection
Advanced cluster features including DRS, high availability, and fault tolerance

Beginning with vSphere 6.0, vCenter Server and the appliance alternative have the same limitations and features. Previous versions were intended for smaller setups, as they missed support for multiple linked (Linked Mode) or clustered (vCenter Heartbeat) vCenter Server instances.

Introduction to vCenter Server

To start with, vCenter Server is the centralized management utility by VMware, and is used to manage virtual machines, multiple ESXi hosts, and all dependent components from a single centralized location. Using this tool, you're also able to take full control of advanced components including distributed switches, vMotion, Storage vMotion, templates, and clones.

vCenter Server architecture

In order to understand how vCenter Server works, it is important to understand its architecture.

The vCenter Server architecture is made up of the following components:

vSphere Web Client and vSphere Client: As discussed in the previous chapter, VMware offers both vSphere Web Client and vSphere legacy client to manage ESXi hosts and virtual machines. The vSphere legacy client can be used to connect directly to an ESXi host or to vCenter Server, but vSphere Web Client is used to connect only to the vCenter Server, not individual ESXi hosts.
- The recommendation from VMware is to use VMware vCenter Server to manage ESXi hosts and virtual machines, and therefore use vSphere Web Client, as all the new features are available only through the use of vSphere Web Client. New customers should start with vSphere Web Client in any case, as VMware plans to give up the legacy client some day.
vCenter Server database: It is the most crucial component of the architecture. It stores...

Communication between vCenter Server and ESXi hosts

The main service running on the vCenter Server is known as vpxd or VMware Virtual Server service. When an ESXi host is added to the vCenter Server, there is an agent service called vpxa, which is installed and started on the ESXi host. Vpxa acts as an intermediary service between the vpxd service running on the vCenter Server and hostd service running on the ESXi host. The hostd service running on the ESXi host is mainly responsible for managing most of the operations on the host.

It knows all the registered virtual machines, their status, and the storage volumes that are visible to the host. When commands such as creating, migrating, or suspending a virtual machine from vCenter Server is issued, the vpxd service running on the vCenter Server sends the command to vpxa, and vpxa in turn forwards it to hostd, which then executes the command.

If a command is issued through the vCenter Server, the vCenter Server database is also updated. vCenter...

Additional vCenter Server components

vCenter Server also consists of the following services and interfaces:

Core services: This includes managing resources and virtual machines, scheduling tasks, managing and generating events and alarms, and logging statistics. It also offers functionality for provisioning virtual machines and configuring hosts.
Distributed services: This offers functionality for serving vSphere clusters, including (storage) vMotion, (storage) DRS, and high availability. While vMotion and storage vMotion are used for migrating virtual machines and their virtual hard disks online, DRS and Storage DRS implement automatic load balancing of computing and storage resources. vSphere high availability makes sure that virtual machines are restarted as fast as possible when an ESXi host crash happens.
Additional services: vCenter Server can be integrated with additional VMware products, including vSphere Update Manager (vUM) or vCenter Orchestrator. Some additional components like...

Comparison of vCenter Server and vCenter Server Appliance

In order to manage your virtualized data center, you are provided with some alternatives to install vCenter Server:

Installation on a supported Windows-based operating system
Deployment as a Linux-based virtual appliance (vCSA)

Both variants are quite similar as they both offer a wide range of management functionality, including:

Deployment and management of virtual machines, templates, and OVF appliances
Management of multiple ESXi hosts
Centralized network and storage provisioning
Statistics and performance data collection
Advanced cluster features including DRS, high availability, and fault tolerance

Beginning with vSphere 6.0, vCenter Server and the appliance alternative have the same limitations and features. Previous versions were intended for smaller setups, as they missed support for multiple linked (Linked Mode) or clustered (vCenter Heartbeat) vCenter Server instances.

Preparing and installing vCenter Server on Microsoft Windows

vCenter Server is probably still, mostly installed on servers running Microsoft Windows. Before installing the application, it is important to ensure that all requirements are met.

Hardware, software, and network requirements

Assuming that all major vCenter Server components should be installed on one single host, the requirements are:

64-bit compatible processor with at least 2 logical cores and 2 Ghz
At least 12 GB memory
At least 100 GB hard drive capacity
64-bit variant of Microsoft Windows Server (2008 SP2 or newer)
64-bit database Open Database Connectivity (ODBC) driver and Data Source Name (DSN) for establishing database connection
1 GBit/s network
Resolvable system hostname using DNS forward and reverse lookup

For alternate setup scenarios, requirements might differ. The vCenter Server documentation offers very detailed lists of recommendations and requirements for particular infrastructure scenarios.

Database preparation

In order...

Importing, starting, and configuring the vCenter Server Appliance

When a user logs in into any of the above platforms using the vSphere client interface, he/she gets an indistinguishable difference. Because of this, the user does not come to know the platform on which the vCenter Server service is running.

The time required to deploy vCenter Server and its associated services is reduced by vCenter Server Appliance. It is also a low-cost alternative as there is no additional operating system license cost associated with VMware vCenter Server Appliance.

vCenter Server Appliance features

vCenter Server Appliance includes a prepackaged vCenter Server setup in SUSE Linux Enterprise Server 11 for vSphere operating system. It also comes with a PostgreSQL server derivate called vPostgres. For vCenter Server 5.5, this is supported by: