It appears that a virtual machine (VM) in a DRS Cluster is having performance problems
because it does not have enough CPU resources available.
Which of the following methods could be used to improve performance and reduce CPU
contention of this VM while maintaining compatibility with DRS (Choose Two)?

A.
increase CPU shares for this VM to High

B.
set the CPU reservation for this VM to the Average CPU Utilization and the CPU limit
for this VM to
Peak CPU Utilization

C.
set CPU affinity on the VM

D.
set the CPU reservation for this VM to 100%

Explanation:
Assume the VMs CPU usage on the host looks like this currently

Assume the cluster has 4000 GHz total CPU available, and that currently the VM has
1000 MHz reserved to it, and peaks at 2000 MHz.

vSphere Basic System Administration vCenter Server 4.0 ESX 4.0 ESXi 4.0, page 155.

The values Low, Normal, High, and Custom are compared to the sum of all shares of all
virtual machines on the server. Therefore if you increase CPU shares for this VM to
High, it will gain proportionally more resources, improve performance and reduce CPU
contention. Therefore A is correct.

If you set the CPU reservation for this VM to the Average CPU Utilization, (which will
be a value between 1000 MHz and 2000 MHz) and the CPU limit for this VM to Peak
CPU Utilization 2000 MHz. This will cause the VM to gain additional resources, and
should improve performance. Therefore B is correct.

Affinity rules
In general, don’t specify affinity rules unless you have specific reasons to do so. This will
give DRS the maximum flexibility to consider all options for resource management and
hence enable the most efficient resource placement. Setting CPU affinity will not
increase available resources. Therefore C is incorrect.

Resource Management and DRS Best Practices
The following guidelines can help you achieve optimal performance for your virtual
machines:

When specifying the reservations for virtual machines, always leave some headroom; do
not commit all resources. As you move closer to fully reserving all capacity in the
system, it becomes increasingly difficult to make changes to reservations and to the
resource pool hierarchy without violating admission control. In a DRS-enabled cluster,
reservations that fully commit the capacity of the cluster or of individual hosts in the
cluster can prevent DRS from migrating virtual machines between hosts. Therefore D is
incorrect.