XenCenter

Adjusting the Optimization Mode

Workload Balancing makes recommendations to rebalance, or optimize, the virtual machine workload in your environment based on a strategy for placement you select known as the optimization mode.

Maximum Density and Maximum Performance modes

You can select one of two optimization modes:

  • Maximize Performance. (Default.) Workload Balancing attempts to spread the workload evenly across all physical hosts in a resource pool. The goal is to minimize CPU, memory, network, and disk pressure for all hosts. When Maximize Performance is your placement strategy, Workload Balancing recommends an optimization when a virtual machine reaches the High threshold.
  • Maximize Density. Workload Balancing attempts to fit as many virtual machines as possible onto a physical host. The goal is to minimize the number of physical hosts that must be online.

    When you select Maximize Density as your placement strategy, you can specify rules similar to the ones in Maximize Performance. However, Workload Balancing uses these rules to determine how it can pack virtual machines onto a host. When Maximize Density is your placement strategy, Workload Balancing recommends an optimization when a virtual machine reaches the Critical threshold.

Workload Balancing also lets you apply these optimization modes always, Fixed, or switch between modes for specified time periods, Scheduled.

Fixed

Fixed optimization modes always set Workload Balancing to a specific optimization behavior - either to try to create the best performance or the highest density.

Scheduled

Scheduled optimization modes let you schedule for Workload Balancing to apply different optimization modes depending on the time of day. For example, you can configure Workload Balancing to optimize for performance during the day when you have users connected. Then you can save energy by specifying for Workload Balancing to optimize for Maximum Density at night.

When you configure Scheduled optimization modes, Workload Balancing automatically changes to the optimization mode at the beginning of the time period that you specified.

To set an optimization mode for all time periods

  • Select the pool in the Resources pane, select the WLB tab, and then select Settings.
  • In the left pane, select Optimization Mode.
  • Select Fixed, and select one of these optimization modes:
    • Maximize Performance. (Default.) Attempts to spread the workload evenly across all physical hosts in a resource pool. The goal is to minimize CPU, memory, network, and disk pressure for all hosts.
    • Maximize Density. Attempts to fit as many virtual machines as possible onto a physical host. The goal is to minimize the number of physical hosts that must be online. (Workload Balancing considers the performance of consolidated VMs and issues a recommendation to improve performance if a resource on a host reaches a Critical threshold.)

To specify times when the optimization mode changes automatically

  • Select the pool in the Resources pane, select the WLB tab, and then select Settings.
  • In the left pane, select Optimization Mode.
  • Select Scheduled.
  • Select Add New to open the Optimization Mode Scheduler dialog box.
  • Select an optimization mode in the Change to list box:
    • Maximize Performance. Attempts to spread the workload evenly across all physical hosts in a resource pool. The goal is to minimize CPU, memory, network, and disk pressure for all hosts.
    • Maximize Density. Attempts to fit as many virtual machines as possible onto a physical host. The goal is to minimize the number of physical hosts that must be online.
  • Select the day of the week and the time when you want Workload Balancing to begin operating in this mode.
  • Create more scheduled mode changes (that is, “tasks”) until you have the number you need. If you only schedule one task, Workload Balancing switches to that mode and never switch back.
  • Select OK.

To delete or pause a scheduled optimization mode task

  1. Select the pool in the Resources pane, select the WLB tab, and then select Settings.
  2. Select Optimization Mode.
  3. Select a scheduled task and select one of the following:

    • Delete the task permanently. Select the Delete button.
    • Stop the task from running temporarily. Right-click the task and select Disable.

    To re-enable a task, right-click the task in the Scheduled Mode Changes list.

To edit a scheduled optimization mode task

  1. Select the pool in the Resources pane, select the WLB tab, and then select Settings.
  2. Select a scheduled task.
  3. Select Edit.
  4. In the Change to box, select a different mode or make other changes as desired.