DRS does not perform vMotion when problems occur on the cluster.

DRS never performs vMotion for the following reasons:

DRS is disabled on the cluster.

The hosts do not have shared storage.

The hosts in the cluster do not contain a vMotion network.

DRS is manual and nobody approves the move.

DRS seldom performs vMotion for the following reasons:

Loads are unstable, or vMotion takes a long time, or both. A move is not appropriate.

DRS seldom or never migrates virtual machines.

DRS moves virtual machines for the following reasons:

Evacuation of host that a user requested enter maintenance or standby mode.

VM/Host DRS rules or VM/VM DRS rules.

Reservation violations.

Load imbalance.

Power management.

DRS migration threshold is set too high.