VMware View deployments can use VMware HA clusters to guard against physical server failures. Because of View Composer limitations, the cluster must contain no more than 8 servers, or nodes.

VMware vSphere and vCenter provide a rich set of features for managing clusters of servers that host View desktops. The cluster configuration is also important because each View desktop pool must be associated with a vCenter resource pool. Therefore, the maximum number of desktops per pool is related to the number of servers and virtual machines that you plan to run per cluster.

In very large VMware View deployments, vCenter performance and responsiveness can be improved by having only one cluster object per datacenter object, which is not the default behavior. By default, VMware vCenter creates new clusters within the same datacenter object.

VMware vSphere, through its efficiency and resource management, lets you achieve industry-leading levels of virtual machines per server. But achieving a higher density of virtual machines per server means that more users are affected if a server fails.

Requirements for high availability can differ substantially based on the purpose of the desktop pool. For example, a stateless desktop image (floating-assignment) pool might have different recovery point objective (RPO) requirements than a stateful desktop image (dedicated-assignment) pool. For a floating-assignment pool, an acceptable solution might be to have users log in to a different desktop if the desktop they are using becomes unavailable.

In cases where availability requirements are high, proper configuration of VMware HA is essential. If you use VMware HA and are planning for a fixed number of desktops per server, run each server at a reduced capacity. If a server fails, the capacity of desktops per server is not exceeded when the desktops are restarted on a different host.

For example, in an 8-host cluster, where each host is capable of running 128 desktops, and the goal is to tolerate a single server failure, make sure that no more than 128 * (8 - 1) = 896 desktops are running on that cluster. You can also use VMware DRS (Distributed Resource Scheduler) to help balance the desktops among all 8 hosts. You get full use of the extra server capacity without letting any hot-spare resources sit idle. Additionally, DRS can help rebalance the cluster after a failed server is restored to service.

You must also make sure that storage is properly configured to support the I/O load that results from many virtual machines restarting at once in response to a server failure. Storage IOPS has the most effect on how quickly desktops recover from a server failure.

The settings listed in HA Cluster Example are VMware View-specific. For information about limits of HA clusters in vSphere, see the VMware vSphere Configuration Maximums document.

HA Cluster Example

Item

Example

Nodes (ESX/ESXi hosts)

8 (including 1 hot spare)

Cluster type

DRS (Distributed Resource Scheduler)/HA

Networking component

Standard ESX/ESXi 4.1 cluster network

Switch ports

80

Networking requirements depend on the type of server, the number of network adapters, and the way in which vMotion is configured.