A new ESX Server is set up initially with two virtual machines (VMs) for users to access. The applications will allocate all the memory that is available to them. 20 identical VMs will be installed within six months, which may lead to memory contention. How can the first two VMs be configured so that their performance does not decrease as more VMs are added?

A.
set the memory shares so that the VMs get 10 shares per megabyte of configured memory for the VMs

B.
set a memory limit on the VMs that is a lower value than the configured memory for the VMs

C.
set an expandable memory reservation on the VM that is lower than 50% of the configured memory for the VMs

D.
set a memory reservation on the VMs that is lower than 50% of the configured memory for the VMs

Explanation:
vSphere Resource Management Guide ESX 4.0 ESXi 4.0 vCenter Server 4.0, page 24.

At present each virtual machine will potentially gain access to 50% of the available physical memory. Once the additional 20 virtual machines have been provisioned, each virtual machine will average approximately 4% of the available physical memory.

A memory limit is an upper bound on the amount of physical memory that the host can allocate to the virtual machine. The virtual machine’s memory allocation is also implicitly limited by its configured size.

Therefore if a memory limit is imposed, it could be used to limit the available memory to a similar value to that available once the additional 20 virtual machines are added.