2.2.2. Cluster Operations

Creating a New Host Cluster
Before creating a new cluster, ensure that there is at least one host available to be assigned to it. The hosts in a cluster all run the same type of CPU.


The default rhevm network cannot be modified once a cluster has been attached to a data center. Any configuration required for the rhevm network, such as enabling VLAN tagging, must be performed before a cluster is attached, and the data center is still in the Uninitialized state.
Perform the following steps to create a new cluster:
  1. On the Tree pane, click the + sign next to the System tab. A list of data centers displays. Select the required Data Center from this list.
  2. Open clusters by either expanding the required Data Center tab in the Tree pane and clicking on Clusters or select Clusters from the Details pane.
  3. Click the New button. The New Cluster dialog box displays.
  4. On the General tab, perform the following:

    General Tab

    1. The Data Center field should be pre-selected and disabled because you are already in the required Data Center.
    2. Enter the cluster Name and Description. The name cannot include spaces.
    3. Select the CPU Name for hosts in this cluster. All hosts must run the same type of CPU. The CPU Name list displays all the CPU types supported by Red Hat Enterprise Virtualization. Finally on the General tab, select the Compatibility Level of the data center, from either 2.2 or 3.0.
  5. The second option in New Cluster window is Memory Optimization.

    Memory Optimization

    1. Use the Memory Optimization tab to define how much of the host's memory can be used in excess of the permitted memory for a virtual machine in the cluster. For example, all virtual machines will not be using the full amount of allocated memory all the time. Memory sharing allows virtual machines that require additional memory at a certain time to use memory that is not being used at that time by other virtual machines. This feature allows you to fine tune how you wish to optimize the memory page sharing and large pages implementation on the hosts in the cluster. Memory Optimization enables you to optimize for density and performance.
    New Cluster - Memory Optimization

    Figure 2.10. New Cluster - Memory Optimization

  6. The third option in New Cluster window is Resilience Policy.

    Resilience Policy

    1. Select the Resilience Policy tab to define if high availability is to be implemented for the virtual machines in the cluster. If a host shuts down unexpectedly or is put into maintenance, the virtual machines running on the host can be re-run on another host in the same cluster. This field allows you to configure the migration settings for virtual machines.
    2. Select from Migrate Virtual Machines, (migrates all machines); Migrate only Highly Available Virtual Machines or Do Not Migrate Virtual Machines.
    New Cluster - Resilience Policy

    Figure 2.11. New Cluster - Resilience Policy

  7. Click OK to create the cluster. The new host cluster is added to the data center and displays on the Clusters tab.
    The New Cluster - Guide Me dialog box displays. For more information on this feature, see Section 1.1.2, “Using the Guide Me facility”.
  8. The Guide Me dialog box prompts you to add hosts to the new cluster. Click the Configure Hosts button, the New Host dialog box displays.
    Enter the details of the host to assign to the cluster. Click OK to close the New Host dialog box and return to the Clusters tab. The Hosts tab on the Details pane displays the newly added hosts. Adding hosts is described in Chapter 4, Red Hat Enterprise Virtualization Hosts.