6.7

Table Of Contents
Figure 111. Load Balancing
Host 1
VM1
VM4
VM2 VM3
VM5 VM6
Host 2
VM7
Host 3
VM8 VM9
Host 1
VM1 VM2 VM3
Host 2
VM7 VM4 VM5
Host 3
VM8 VM9 VM6
When a cluster becomes unbalanced, DRS makes recommendations or migrates virtual machines,
depending on the default automation level:
n
If the cluster or any of the virtual machines involved are manual or partially automated,
vCenter Server does not take automatic actions to balance resources. Instead, the Summary page
indicates that migration recommendations are available and the DRS Recommendations page
displays recommendations for changes that make the most efficient use of resources across the
cluster.
n
If the cluster and virtual machines involved are all fully automated, vCenter Server migrates running
virtual machines between hosts as needed to ensure efficient use of cluster resources.
Note Even in an automatic migration setup, users can explicitly migrate individual virtual machines,
but vCenter Server might move those virtual machines to other hosts to optimize cluster resources.
By default, automation level is specified for the whole cluster. You can also specify a custom automation
level for individual virtual machines.
DRS Migration Threshold
The DRS migration threshold allows you to specify which recommendations are generated and then
applied (when the virtual machines involved in the recommendation are in fully automated mode) or
shown (if in manual mode). This threshold is also a measure of how much cluster imbalance across host
(CPU and memory) loads is acceptable.
vSphere Resource Management
VMware, Inc. 72