How to Create a VMware Cluster

Managing multiple ESX Servers is easy with the VMware. This excerpt from Troy & Helmke's VMware Cookbook will guide you through the process of creating a cluster with the vCenter client.

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If you want to create a cluster to manage the resources offered by the multiple ESX Servers, use the vCenter client to create the VMware cluster.
Creating a cluster inside vCenter allows you to combine multiple ESX hosts in a centralized group, placing all of their CPU and memory resources into a general pool for use by virtual machines. When you add an ESX host to a cluster, the resources will automatically become available for use by the virtual machines.
For example, Figure 4.12 shows six ESX hosts, each of which has 64GB of memory and two quad-core CPUs (i.e., eight CPUs per ESX host, for a total of 48). Because clustering pools the resources, you effectively have an enormous unified pool of CPUs and memory for the virtual machines to run. Combining a cluster with HA and DRS will further enhance your environment.

Figure 4.12. VMware cluster overview

Note

You do not need a license to create ESX clusters. However, to take advantage of HA and DRS you will need to obtain a license key from VMware.

VMware allows for a maximum of 16 ESX hosts in a vCenter 2.5x cluster. In vCenter 4.x you can have up to 32 ESX hosts in a cluster.
VMware has done a really nice job of making it simple to add a new cluster in vCenter:

1. Load the vCenter client and log into your vCenter server.
2. Right-click on the datacenter name and select New Cluster, as shown in Figure 4.13.
   The New Cluster wizard will launch to guide you through the process of creating the new cluster. The first screen in the wizard will ask you to enter a name for the cluster and indicate whether or not to enable two features:
   

   VMware HA

   This feature is available only to users who have a license for the HA product extension. When you enable VMware HA, it will detect and provide rapid recovery of virtual machines if an ESX host fails. This is an optional feature and doesn’t need to be enabled to create a basic cluster.

   VMware DRS

   This feature also requires a license. DRS allows vCenter server to manage hosts as an aggregate pool of resources. Clusters can be broken down into smaller groups by using resource pools. VMware DRS also allows vCenter to manage resources on virtual machines, even placing them on different hosts if used in conjunction with VMotion. This is an optional feature that is not required to create a cluster.

   When you’ve made your selections, press the Next button to continue. Additional cluster features (including DRS and HA) can be enabled or disabled at a later time using processes described elsewhere in this chapter.

Figure 4.13. Adding a new cluster to a datacenter

3. Next, you will be asked where to store the swapfiles for the virtual machines. VMware gives you two options here:
   
   • Store the swapfile in the same directory as the virtual machine. (Recommended.)
   • Store the swapfile in the datastore specified by the host. (This option is not recommended because you could experience degraded performance.)
   Make your selection, then press the Next button to continue.
4. Finally, review the summary and click Finish to initiate the build of the cluster.

You can now add ESX hosts to the cluster.