Workload Balancing


  • Workload Balancing is available for XenServer Premium Edition customers. For more information about XenServer licensing, see Licensing. To upgrade, or to get a XenServer license, visit the XenServer website.
  • Workload Balancing 8.3.0 and later are compatible with XenServer 8. If you perform a rolling pool upgrade from Citrix Hypervisor 8.2 CU1 to XenServer 8, you cannot use Workload Balancing 8.2.2 with your XenServer 8 pools. Update the Workload Balancing virtual appliance to 8.3.0 before performing the rolling pool upgrade. You can download the latest version of the Workload Balancing virtual appliance from the XenServer Downloads page.

Workload Balancing is a XenServer Premium Edition component, packaged as a virtual appliance, that provides the following features:

  • Create reports about virtual machine (VM) performance in your XenServer environment

  • Evaluate resource utilization and locates VMs on the best possible hosts in the pool for their workload’s needs

  • Balance VM workloads across hosts in a XenServer resource pool

  • Determine the best host on which to start a VM

  • Determine the best host on which to resume a VM that you powered off

  • Determine the best host to move a VM to when a host fails

  • Determine the optimal server for each of the host’s VMs when you put a host into or take a host out of maintenance mode

Depending on your preference, Workload Balancing can accomplish these tasks automatically or prompt you to accept its rebalancing and placement recommendations. You can also configure Workload Balancing to power off hosts automatically at specific times of day. For example, configure your hosts to switch off at night to save power.

Workload Balancing can send notifications in XenCenter regarding the actions it takes. For more information on how to configure the alert level for Workload Balancing alerts by using the xe CLI, see Set alert level for Workload Balancing alerts in XenCenter.

Workload Balancing functions by evaluating the use of VMs across a pool. When a host exceeds a performance threshold, Workload Balancing relocates the VM to a less-taxed host in the pool. To rebalance workloads, Workload Balancing moves VMs to balance the resource use on hosts.

To ensure that the rebalancing and placement recommendations align with your environment’s needs, you can configure Workload Balancing to optimize workloads in one of the following ways:

  • To maximize resource performance
  • To maximize the number of VMs that fit on hosts

These optimization modes can be configured to change automatically at predefined times or stay the same always. For extra granularity, fine-tune the weighting of individual resource metrics: CPU, network, disk, and memory.

To help you perform capacity planning, Workload Balancing provides historical reports about host and pool health, optimization and VM performance, and VM motion history.

As Workload Balancing captures performance data, you can also use this component to generate reports, known as Workload Reports, about your virtualized environment. For more information, see Generate workload reports.

Workload Balancing basic concepts

When VMs are running, they consume computing resources on the physical host. These resources include CPU, Memory, Network Reads, Network Writes, Disk Reads, and Disk Writes. Some VMs, depending on their workload, might consume more CPU resources than other VMs on the same host. Workload is defined by the applications running on a VM and their user transactions. The combined resource consumption of all VMs on a host reduces the available resources on the host.

Workload Balancing captures data for resource performance on VMs and physical hosts and stores it in a database. Workload Balancing uses this data, combined with the preferences you set, to provide optimization and placement recommendations.

Optimizations are a way in which hosts are “improved” to align with your goals: Workload Balancing makes recommendations to redistribute the VMs across hosts in the pool to increase either performance or density. When Workload Balancing is making recommendations, it makes them in light of its goal: to create balance or harmony across the hosts in the pool. If Workload Balancing acts on these recommendations, the action is known as an optimization.

When Workload Balancing is enabled, XenCenter provides star ratings to indicate the optimal hosts for starting a VM. These ratings are also provided:

  • When you want to start the VM when it is powered off
  • When you want to start the VM when it is suspended
  • When you want to migrate the VM to a different host (Migrate and Maintenance Mode)

Within a Workload Balancing context:

  • Performance is the usage of physical resources on a host (for example, the CPU, memory, network, and disk utilization on a host). When you set Workload Balancing to maximize performance, it recommends placing VMs to ensure that the maximum amount of resources are available for each VM.

  • Density is the number of VMs on a host. When you set Workload Balancing to maximize density, it recommends placing VMs so you can reduce the number of hosts powered on in a pool. It ensures that the VMs have adequate computing power.

Workload Balancing does not conflict with settings you already specified for High Availability: these features are compatible.

Workload Balancing