Planning for Host Groups

A virtual machine host is a physical computer that hosts one or more virtual machines.

You can organize hosts into host groups, which provide ease of monitoring and management of hosts and virtual machines. You can use host groups to organize hosts in whatever manner makes sense for your environment.

How Should I Use Host Groups?

A host group's most basic function is as a container that you can use to group hosts and the virtual machines on those hosts in a meaningful way in Hosts view and Virtual Machines view. You can also use host groups to:

• Configure host reserves, which are resources that are set aside for the use of the host operating system.

• Designate which hosts are for self-service users.

• Designate which hosts are connected to a storage area network (SAN) infrastructure.

  Note

  This designation is a best practice if you use a SAN.

• Enable automatic placement of virtual machines on the best host in a group of hosts.

You can create host groups to organize hosts in whatever manner makes sense for your environment.

The following list provides some examples of how you might organize host groups. You can also use a combination of these by creating hierarchical child host groups, as described later in this topic.

• Basic organization when managing large numbers of hosts and virtual machines—Use host groups to create custom views within Hosts view and Virtual Machines view to provide fast monitoring and access to host groupings of your choice. For example, you might create host groups:
  • For branch offices in your organization.
  • To match your Active Directory structure.
  • To reflect functions within your environment such as development, test, production, or research.
• Scoping administrative tasks such as the placement of virtual machines on hosts—You can limit the hosts examined for an administrative task by creating a host group. For example, restrict the placement of a virtual machine by selecting a particular host group.
• Reserving resources for use by hosts—Host reserves become useful when virtual machines are placed on a host. The host reserves determine the amount of CPU, memory, disk space, disk I/O capacity, and network capacity that will always be available to the host operating system. Use the Host group properties action for the root host group, All Hosts, to set default host reserves for all hosts managed by Virtual Machine Manager. If you want to use the resources on some hosts more fully than on others, you can set host reserves for other host groups.
• Automatically placing virtual machines on the most suitable host—In Virtual Machines view, you can drag a virtual machine to a host group to automatically place the virtual machine on the most suitable host in a host group. Automatic placement is also used to deploy the virtual machines that users create in virtual machine self-service. For more information, see the "About Virtual Machine Placement" topic in VMM Help (https://go.microsoft.com/fwlink/?LinkId=98982).
• Designating self-service hosts on which users can create and operate their own virtual machines—This feature is known as virtual machine self-service. The administrator adds self-service policies to a host group to enable users or groups to create, operate, and manage their own virtual machines within a controlled environment on the hosts in the host group. For more information, see the "About Virtual Machine Self-Service" topic in VMM Help (https://go.microsoft.com/fwlink/?LinkId=98644).

Creating a Host Group Hierarchy

Host groups are hierarchical. You can create a child host group of an existing host group for general management purposes, to override host reserves inherited from a parent host group, or to amend or add to the virtual machine permissions inherited from the self-service policies of a parent host group.

All host groups and all hosts belong to the root host group, All Hosts, which is created during installation and is represented by the top node in Hosts view and Virtual Machines view.

Each host or host group is identified by its host path, a sequence of host group names that specifies the location of a host or host group within the hierarchy of host groups in the navigation pane. All host paths begin with the root host group. For example, the host path All Hosts\New York\Site21\VMHost05 indicates that the host VMHost05 belongs to the host group Site21, which is a child host group of the host group New York.

Inheritance of Host Group Properties

Child host groups can inherit host reserve settings and self-service policies from their parent host groups. However, property inheritance works differently for these two features:

• Host reserves—When you change the host reserves for a parent host group, you can choose whether or not to cascade the host reserve settings to hosts in all of its child host groups. If you choose to cascade the host reserve settings, all of the host reserve settings for the parent host group overwrite all previous settings for all hosts in all of the child host groups of the parent host group.

  Note

  When you cascade host reserve settings to child host groups, the changes to the child host groups are not audited on the Change Tracking tab in the job details.

• Self-service policies—If a parent host group is used for virtual machine self-service, each of its child host groups automatically inherits self-service policies from the parent host group. However, you can add a self-service policy for the same user or group to both a parent host group and its child host group. By adding policies to both parent and child, you can assign the same users different templates, set different virtual machine permissions, and assign a different virtual machine quota on a subset of hosts within the parent host group.

Virtual Machine Self-Service

One important use of host groups is for administering virtual machine self service. Self-service enables the VMM administrator to grant users permission to create, operate, and manage their own virtual machines within a controlled environment and only on hosts within a specified host group.

To control how self-service users create, operate, and manage virtual machines, the administrator adds self-service policies to a host group. For more information about virtual machine self service, see the "About Virtual Machine Self-Service" topic in VMM Help (https://go.microsoft.com/fwlink/?LinkId=98644).

Isolate a Host

You can use a host group to isolate a host. For example, if you have a host with guest operating systems that are running mission-critical applications, you can isolate that host by placing it in its own host group. This way you can ensure that there are no self-service policies applied on the host group and that the system resources set aside for running the host's operating system are appropriate, thus maximizing the host resources available for use by the guest operating systems.

See Also

Concepts

Planning for Hosts
Planning for VMM Components and Features
Planning for VMM Deployment
Introducing Virtual Machine Manager