VCenter Server is a service that acts as a central administrator for ESXi hosts that are connected on a network. VCenter Server allows you to pool and manage the resources of multiple hosts.
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.
You can join multiple vCenter Server systems using Linked Mode to allow them to be managed using a single vSphere Client connection.
Good To Know
When you first log in to the vSphere Client, it displays a Home page with icons that you select to access vSphere Client functions. When you log out of the vSphere Client, the client application retains the view that was displayed when it closed, and returns you to that view when you next log in.
vCenter Server plug-ins
Plug-ins are applications that provide additional features and functionality to vCenter Server. Typically, plug-ins consists of a server component and a client component. While installing the Plug-in Server software, it requests a vCenter Name/Credentials, this step allows server component to be registered to vCenter and the plug-in client is available to vSphere clients for download. After the server component of a plug-in is installed and registered with vCenter Server, its client component is available to vSphere clients. 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, therefore do not need to install any server component. It can be managed using the vSphere Client Plug-in Manager. These features are
1. vCenter Storage Monitoring
2. vCenter Hardware Status, and
3. vCenter Service Status.
Tomcat Web server (VCTOMCAT)
Many vCenter Server functions are implemented as Web services that require the Tomcat Web server. The Tomcat Web server installation is integrated in the vCenter Server installation and therefore do not need to installed separately.
Features that require the Tomcat Web server to be running include:
1. Linked Mode
2. CIM/Hardware Status tab
3. Performance charts
5. vCenter Storage Monitoring/Storage Views tab, and
6. vCenter Service status
vSphere Managed Inventory Objects
In vSphere, the inventory is a collection of virtual and physical objects on which you can place permissions, monitor tasks and events, and set alarms. You can group most inventory objects by using folders to more easily manage them. vCenter Server objects are datacenters, networks, datastores, resource pools, clusters, hosts, and virtual machines.
All inventory objects, with the exception of hosts, can be renamed to represent their purposes.
PZ Notes: I have included only those objects which have information which is new to me and worth remembering. If you need to read whole page refer page 14 of vCenter Server and Host management guide
Unlike a folder, which is used to organize a specific object type, a datacenter is an aggregation of all the different types of objects needed to do work in virtual infrastructure: hosts, virtual machines, networks, and datastores.
Within a datacenter there are four separate hierarchies.
The datacenter defines the namespace for networks and datastores. The names for these objects must be unique within a datacenter.
For example, you cannot have two datastores with the same name within a single datacenter, but you can have two datastores with the same name in two different datacenters.
Virtual machines, templates, and clusters need not be unique within the datacenter, but must be unique within their folder. Objects with the same name in two different datacenters are not necessarily the same object.
For example, a network named network A in datacenter A might not be the same network as a network named network A in datacenter B. Therefore moving a virtual machine connected to network A from datacenter A to datacenter B results in the virtual machine changing the network it is connected to.
Folders allow you to group objects of the same type so you can easily manage them. Within each datacenter is one hierarchy of folders with virtual machines and templates, one with hosts and clusters, one with datastores, and one with networks.
A folder can contain other folders, or a group of objects of the same type: datacenters, clusters, datastores, networks, virtual machines, templates, or hosts.
For example, one folder can contain hosts and a folder containing hosts, but it cannot contain hosts and a folder containing virtual machines.
You can use folders to set permissions across objects, to set alarms across objects, and to organize objects in a meaningful way.
All virtual machines that connect to the same port group belong to the same network in the virtual environment, even if they are on different physical servers. You can monitor networks and set permissions and alarms on port groups and distributed port groups.
Resource pools are used to compartmentalize the CPU and memory resources of a host or cluster. Virtual machines execute in, and draw their resources from, resource pools. You can create multiple resource pools as direct children of a standalone host or cluster and then delegate control over them to other individuals or organizations.
A feature that enables you to manage multiple datastores as a single compute resource, called a datastore cluster. A datastore cluster is an aggregation of multiple datastores into a single logical, load-balanced pool. You can treat the datastore cluster as a single flexible storage resource for resource management purposes. You can assign a virtual disk to a datastore cluster, and Storage DRS finds an appropriate datastore for it.