6.7

Table Of Contents
You can move the threshold slider to use one of five settings, ranging from Conservative to Aggressive.
The five migration settings generate recommendations based on their assigned priority level. Each setting
you move the slider to the right allows the inclusion of one more lower level of priority. The Conservative
setting generates only priority-one recommendations (mandatory recommendations), the next level to the
right generates priority-two recommendations and higher, and so on, down to the Aggressive level which
generates priority-five recommendations and higher (that is, all recommendations.)
A priority level for each migration recommendation is computed using the load imbalance metric of the
cluster. This metric is displayed as Current host load standard deviation in the cluster's Summary tab in
the vSphere Client. A higher load imbalance leads to higher-priority migration recommendations. For
more information about this metric and how a recommendation priority level is calculated, see the
VMware Knowledge Base article "Calculating the priority level of a VMware DRS migration
recommendation."
After a recommendation receives a priority level, this level is compared to the migration threshold you set.
If the priority level is less than or equal to the threshold setting, the recommendation is either applied (if
the relevant virtual machines are in fully automated mode) or displayed to the user for confirmation (if in
manual or partially automated mode.)
Migration Recommendations
If you create a cluster with a default manual or partially automated mode, vCenter Server displays
migration recommendations on the DRS Recommendations page.
The system supplies as many recommendations as necessary to enforce rules and balance the
resources of the cluster. Each recommendation includes the virtual machine to be moved, current
(source) host and destination host, and a reason for the recommendation. The reason can be one of the
following:
n
Balance average CPU loads or reservations.
n
Balance average memory loads or reservations.
n
Satisfy resource pool reservations.
n
Satisfy an affinity rule.
n
Host is entering maintenance mode or standby mode.
Note If you are using the vSphere Distributed Power Management (DPM) feature, in addition to
migration recommendations, DRS provides host power state recommendations.
DRS Cluster Requirements
Hosts that are added to a DRS cluster must meet certain requirements to use cluster features
successfully.
Shared Storage Requirements
A DRS cluster has certain shared storage requirements.
vSphere Resource Management
VMware, Inc. 73