6.7

Table Of Contents
n
Virtual machines are not compatible with the hosts to which DRS would move them. That is, at least
one of the hosts in the cluster is incompatible for the virtual machines that would be migrated. For
example, if host A's CPU is not vMotion-compatible with host B's CPU, then host A becomes
incompatible for powered-on virtual machines running on host B.
n
It would be more detrimental for the virtual machine's performance to move it than for it to run where it
is currently located. This may occur when loads are unstable or the migration cost is high compared
to the benefit gained from moving the virtual machine.
n
vMotion is not enabled or set up for the hosts in the cluster.
Solution
Address the problem that is causing the load imbalance.
Cluster is Yellow
The cluster is yellow due to a shortage of resources.
Problem
If the cluster does not have enough resources to satisfy the reservations of all resource pools and virtual
machines, but does have enough resources to satisfy the reservations of all running virtual machines,
DRS continues to run and the cluster is yellow.
Cause
A cluster can become yellow if the host resources are removed from the cluster (for example, if a host
fails).
Solution
Add host resources to the cluster or reduce the resource pool reservations.
Cluster is Red Because of Inconsistent Resource Pool
A DRS cluster becomes red when it is invalid. It may become red because the resource pool tree is not
internally consistent.
Problem
If the cluster resource pool tree is not internally consistent (for example, the sum of the children's
reservations is greater than the parent pool's nonexpandable reservation), the cluster does not have
enough resources to satisfy the reservations of all running virtual machines making the cluster red.
Cause
This can occur if vCenter Server is unavailable or if resource pool settings are changed while a virtual
machine is in a failover state.
Solution
Revert the associated changes or otherwise revise the resource pool settings.
vSphere Resource Management
VMware, Inc. 141