The virtual machine does not receive enough CPU or memory resources.
In some cases, the virtual machine's demand is greater than its resource entitlement. When this occurs, the virtual machine doesn't receive enough CPU or memory resources.
The following sections describe the factors that influence the entitlement for a virtual machine.
Cluster is Yellow or Red
If the cluster is yellow or red, the capacity is insufficient to meet the resource reservations configured for all virtual machines and resource pools in the cluster. The particular virtual machine might be one that is not receiving its reservation. Check the status of the cluster (red or yellow) and resolve the situation.
Resource Limit is Too Restrictive
The virtual machine, its parent resource pool, or its resource pool ancestors might have a configured resource limit that is too restrictive. Check whether demand is equal to or greater than any configured limits.
Cluster is Overloaded
The cluster on which the virtual machine is running might have insufficient resources. Also, the virtual machine's share value is such that other virtual machines are granted proportionally more of the resources. To determine the demand is larger than the capacity, check the cluster statistics.
Host is Overloaded
To determine if the host's resources are oversubscribed, check the host statistics. If they are oversubscribed, consider why DRS is not moving any of the virtual machines now running on the host to other hosts. This condition might exist for the following reasons:
The VM/VM DRS rules and VM/Host DRS rules require the current virtual machine-to-host mapping. If such rules are configured in the cluster, consider disabling one or more of them. Then run DRS and check whether the situation is corrected.
DRS cannot move this virtual machine or enough of the other virtual machines to other hosts to free up capacity. DRS will not move a virtual machine for any of the following reasons:
DRS is disabled for the virtual machine.
A host device is mounted to the virtual machine.
Either of its resource reservations is so large that the virtual machine cannot run on any other host in the cluster.
The virtual machine is not compatible with any other host in the cluster.
Check whether any of these conditions exist for the virtual machine. If none exist, the conditions might exist for other virtual machines in the cluster. If this is the case, DRS cannot balance the cluster to address the virtual machine's demand.
Decrease the DRS migration threshold setting and check whether the situation is resolved.
Increase the virtual machine's reservation.
Address the problem that is causing the virtual machine to not receive enough CPU or memory resources.