VMware GSX Server 2.5.2

Overview of Clustering with GSX Server

GSX Server clustering capabilities are ideally suited for development, testing and training applications.

Note: Always rigorously test and review your cluster before deploying it in a production environment.

This section includes:

Clustering is providing a service via a group of servers to get high availability, scalability or both.

For example:

In a Web server cluster, where the Web site serves static content, a gateway distributes requests to all nodes according to load. The gateway also redirects requests to remaining nodes if one crashes.

This configuration increases availability and performance over a single-machine approach. Network Load Balancing in Windows 2000 provides such a service.
In a more complex cluster, a single mode might serve a database. If that node crashes, it must restart the database on another node. The database application knows how to recover from a crash. In normal operation, other nodes run other applications.

Microsoft Cluster Service and Veritas Cluster Service provide such a service.

In a typical virtual machine cluster

Each virtual machine is one node in the cluster.
Disks are shared between nodes.
- These are needed if the application uses dynamic data as mail servers or database servers do.
- When using virtual disks, they must be plain disks; see Adding Plain Disks to a Virtual Machine.
There are extra network connections between nodes for monitoring heartbeat status.
There is a method for redirecting incoming requests.

Applications that Can Use Clustering

To take advantage of clustering services, applications need to be clustering aware.

Such applications can be

Stateless, such as Web servers and VPN servers
With built-in recovery features, like those in database servers, mail servers, file servers or print servers

Clustering Software in Virtual Machines

Available clustering software includes:

Microsoft Clustering Service (MSCS)

Provides fail-over support for 2 to 4-node clusters for applications such as databases, file servers and mail servers
Microsoft Network Load Balancing (NLB).

Load balances incoming IP traffic across a cluster of up to 32 nodes for applications such as Web servers and terminal services.
Veritas Clustering Service (VCS)