User's Manual

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The effect of the weighting varies according to the placement strategy you selected. For example, if
you selected Maximum Performance and you set Network Writes towards Less Important, if the
Network Writes on that server exceed the critical threshold you set, Workload Balancing still makes a
recommendation to place a virtual machine's workload on a server but does so with the goal of ensuring
performance for the other resources.
If you selected Maximum Density as your placement recommendation and you specify Network Writes
as Less Important, Workload Balancing will still recommend placing workloads on that host if the Network
Writes exceed the critical threshold you set. However, the workloads are placed in the densest possible way.
By default, all metric weightings are set to the farthest point on the slider (More Important).
To edit metric weighting factors
1. In the Resources pane of XenCenter, select XenCenter > your-resource-pool.
2. In the Properties pane, click the WLB tab.
3. In the WLB tab, click Configure WLB.
4. In the left pane, select Metric Weighting.
5. In Metric Weighting page, if desired, adjust the sliders beside the individual resources.
Moving the slider towards Less Important indicates that ensuring virtual machines always have the
highest amount of this resource available is not as vital on this resource pool.
Excluding Hosts from Recommendations
When configuring Workload Balancing, you can specify that specific physical hosts are excluded
from Workload Balancing optimization and placement recommendations, including Start On placement
recommendations.
Situations when you may want to exclude hosts from recommendations include when:
• You want to run the pool in Maximum Density mode and consolidate and shut down hosts, but there are
specific hosts you want to exclude from this behavior.
• When two VM workloads always need to run on the same host (for example, if they have complementary
applications or workloads).
• You have workloads that you do not want moved around a lot (for example, domain controllers or SQL
Server).
• You want to perform maintenance on a host and you want to leave the host on the network (in the pool).
• The performance of the workload is so critical that the cost of dedicated hardware is irrelevant.
• Specific hosts are running high-priority workloads, which you do not want to prioritize using the High
Availability feature.
• The hardware in the host is not optimum for the other workloads in the pool.
Regardless of whether you specify a fixed or scheduled optimization mode, hosts excluded remain excluded
even when the optimization mode changes. Therefore, if you only want to prevent Workload Balancing from
shutting off a host automatically, consider not enabling (or deselecting) Power Management for that host
instead as described in Optimizing and Managing Power Automatically.
To exclude hosts from placement and optimization recommendations
1. In the Resources pane of XenCenter, select XenCenter > your-resource-pool.