Workload Balancing is a XenServer component, packaged as a virtual appliance, that:
Creates reports about VM performance in your XenServer environment
Evaluates resource utilization and locates virtual machines on the best possible hosts in the pool for their workload’s needs
- Workload Balancing is available for XenServer Enterprise edition customers or those customers who have access to XenServer through their Citrix Virtual Apps and Desktops entitlement.
- Workload Balancing 7.6 is compatible with all supported versions of XenServer and XenServer.
Even if you don’t want to use Workload Balancing to balance your VMs, you might want to run it anyway for the workload reporting feature. When deployed to manage virtual machine workloads, Workload Balancing can:
Balance VM workloads across hosts in a XenServer 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, to save power at night).
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 for either resource performance or 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.
Reports on workloads
Because Workload Balancing captures performance data, you can also use this component to generate reports, known as Workload Reports, about your virtualized environment.
Workload Reports provide data for a pool or host’s health, for auditing, optimizations, and placement (or motion) history. Also, you can run a chargeback report that shows virtual machine usage and can help you measure and assign costs.
To run reports, you do not need to configure for Workload Balancing to make placement recommendations or move virtual machines. However, you must configure the Workload Balancing component. Ideally, you must set critical thresholds to values that reflect the point at which the performance of the hosts in your pool degrades.
For more information, see Generate workload reports.
Workload Balancing basic concepts
When virtual machines are running, they consume computing resources on the physical host, such as CPU, Memory, Network Reads, Network Writes, Disk Reads, and Disk Writes. For example, 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. Naturally, 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.
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: Citrix designed these features to work together.
To balance a pool with Workload Balancing, the hosts in the pool must meet the requirements for XenMotion (live migration), including:
Shared remote storage
Similar processor configurations
If the hosts do not meet these requirements, Workload Balancing cannot migrate the virtual machines in the pool.