When you add a host to a DRS cluster, the host’s resources become part of the cluster’s resources. In addition to this aggregation of resources, with a DRS cluster you can support cluster-wide resource pools and enforce cluster-level resource allocation policies.

Before you begin

You can create a cluster without a special license, but you must have a license to enable a cluster for vSphere DRS (or vSphere HA).

About this task

The following cluster-level resource management capabilities are also available.

Load Balancing

The distribution and usage of CPU and memory resources for all hosts and virtual machines in the cluster are continuously monitored. DRS compares these metrics to an ideal resource usage given the attributes of the cluster’s resource pools and virtual machines, the current demand, and the imbalance target. DRS then provides recommendations or performs virtual machine migrations accordingly. See Virtual Machine Migration. When you power on a virtual machine in the cluster, DRS attempts to maintain proper load balancing by either placing the virtual machine on an appropriate host or making a recommendation. See Admission Control and Initial Placement.

Power management

When the vSphere Distributed Power Management (DPM) feature is enabled, DRS compares cluster and host-level capacity to the demands of the cluster’s virtual machines, including recent historical demand. DRS then recommends you place hosts in standby, or places hosts in standby power mode when sufficient excess capacity is found. DRS powers-on hosts if capacity is needed. Depending on the resulting host power state recommendations, virtual machines might need to be migrated to and from the hosts as well. See Managing Power Resources.

Affinity Rules

You can control the placement of virtual machines on hosts within a cluster, by assigning affinity rules. See Using DRS Affinity Rules.

Procedure

  1. Browse to a cluster in the vSphere Web Client.
  2. Click the Configure tab and click Services.
  3. Under vSphere DRS click Edit.
  4. Under DRS Automation, select a default automation level for DRS.

    Automation Level

    Action

    Manual

    • Initial placement: Recommended host is displayed.

    • Migration: Recommendation is displayed.

    Partially Automated

    • Initial placement: Automatic.

    • Migration: Recommendation is displayed.

    Fully Automated

    • Initial placement: Automatic.

    • Migration: Recommendation is run automatically.

  5. Set the Migration Threshold for DRS.
  6. Select the Predictive DRS check box. In addition to real-time metrics, DRS responds to forecasted metrics provided by vRealize Operations server. You must also configure Predictive DRS in a version of vRealize Operations that supports this feature.
  7. Select Virtual Machine Automation check box to enable individual virtual machine automation levels.

    Override for individual virtual machines can be set from the VM Overrides page.

  8. Under Additional Options, select a check box to enforce one of the default policies.

    Option

    Description

    VM Distribution

    For availability, distribute a more even number of virtual machines across hosts. This is secondary to DRS load balancing.

    Memory Metric for Load Balancing

    Load balance based on consumed memory of virtual machines rather than active memory. This setting is only recommended for clusters where host memory is not over-committed.

    CPU Over-Commitment

    Control CPU over-commitment in the cluster.

  9. Under Power Management, select Automation Level.
  10. If DPM is enabled, set the DPM Threshold.
  11. (Optional) : Select the vSphere HA Turn ON check box to enable vSphere HA.

    vSphere HA allows you to:

    • Enable host monitoring.

    • Enable admission control.

    • Specify the type of policy that admission control enforces.

    • Adjust the monitoring sensitivity of virtual machine monitoring.

  12. If appropriate, enable Enhanced vMotion Compatibility (EVC) and select the mode it operates in.
  13. Click OK.