Workload Balancing is a XenServer appliance that balances your pool by relocating virtual machines onto the best possible servers for their workload in a resource pool. For example, Workload Balancing can:

• Balance virtual-machine 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 power on a virtual machine that you powered off
• Determine the best host for each of the host’s virtual machines when you put that host into Maintenance mode

Note: Workload Balancing is available in Citrix XenServer Enterprise Edition or higher. To learn more about the features available in different XenServer Editions, click here.

Depending on your preference, Workload Balancing can accomplish these tasks automatically or prompt you to accept its optimization, consolidation, and placement recommendations. You can also configure Workload Balancing to power off hosts automatically during periods of low usage (for example, to save power at night).

Workload Balancing evaluates the utilization of virtual-machine workloads across a pool and, when a host reaches one of its thresholds, relocates the virtual machine to a different host in the pool.

To ensure the rebalancing and placement recommendations align with your environment’s needs, you can configure Workload Balancing to optimize workloads for resource performance or to maximize density. These optimization modes can be configured to change automatically at predefined times or stay the same at all times. For additional granularity, you can fine-tune the weighting of individual resource metrics (CPU, network, memory, and disk).

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

workload balancing components:

workload balancing server -xenserver virtual appliance

Data Store -Database server

WLB Virtual Applicance Requirements:

• Communications Port    -Do not set to 443(resource pool uses 443 so dont use it.)
• WLB Service accounts   -WLB account -Database account
• Resource Pools Monitoring
• Self signed SSL Certificate

Optimization Modes:

• Max performance
• Max density
• Optimization modes can be applied on a:   -fixed optimization mode -scheduled optimization mode

Optimization recommendations:

• vm name
• current host
• suggested host
• reason for recommendation

WLB role based access control

Resource Pool Operator:

• Configure, Initialize, enable, disable
• Apply optimization recommendations
• Modify report subscriptions

VM power admin

• Accept placement recommendations

Read only

• Generate reports
• Display configuration

Power Management:

• Power Savings
• XS host power on feature is automatically configured
• Can be set to maximize performance or density, fixed or scheduled
• Apply optimization and power management recommendations automatically

Click here for a documentation on WLB from citrix.