Workload Balancing

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

  • Create reports about VM performance in your Citrix Hypervisor environment

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

  • Balance VM workloads across hosts in a Citrix Hypervisor resource pool

  • Determine the best host on which to start a virtual machine

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

  • Determine the best host to move a virtual machine to when a host fails

  • Determine the optimal server for each of the host’s virtual machines 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 servers to switch off at night to save power.

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 virtual machines 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.

Because 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 is available for Citrix Hypervisor Premium Edition customers or those customers who have access to Citrix Hypervisor through their Citrix Virtual Apps and Desktops entitlement. For more information about Citrix Hypervisor licensing, see Licensing. To upgrade, or to buy a Citrix Hypervisor license, visit the Citrix website.
  • Workload Balancing 8.2.0 and later is compatible with XenServer 7.1 CU2 and Citrix Hypervisor 8.2.
  • To run the latest version of the Workload Balancing virtual appliance on a XenServer 7.1 CU2 host, install Hotfix XS71ECU2040 on the XenServer 7.1 CU2 host. This hotfix enables you to use all Workload Balancing features.

Workload Balancing basic concepts

When virtual machines 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 virtual machines, depending on their workload, might consume more CPU resources than other virtual machines on the same host. Workload is defined by the applications running on a virtual machine and their user transactions. The combined resource consumption of all virtual machines on a host reduces the available resources on the host.

Workload Balancing captures data for resource performance on virtual machines 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 virtual machines 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 virtual machines to ensure that the maximum amount of resources are available for each virtual machine.

  • 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.

Pool requirements

To balance a pool with Workload Balancing, the pool must meet the following requirements:

  • All servers are licensed with a Premium Edition license or a Citrix Virtual Apps and Desktops entitlement

  • All servers meet the requirements for live migration:

    • Shared remote storage

    • Similar processor configurations

    • Gigabit Ethernet

  • The pool does not contain any vGPU-enabled VMs. Workload Balancing cannot create a capacity plan for VMs that have vGPUs attached.

Workload Balancing