A: vSphere 5.0 created quite the brouhaha when IT pros discovered its new vRAM limits. Unlike their terms for previous versions, VMware licenses vSphere 5.0 on a per-processor basis with an assigned vRAM requirement. This vRAM requirement, however, is based specifically on assigned vRAM and not how much of that vRAM is actually used.
Many IT environments assign more memory to VMs than they actually need to perform their job. This over-assignment is understandable because of the flexibility that vSphere provides in terms of memory overcommittment. Consider, for example, the Active Directory domain controller that might be assigned 4GB of vRAM but uses only 1GB of that vRAM during regular operations.
One way to reduce overall costs is to analyze the amount of RAM each workload actually uses and tune the assigned vRAM to match. You can determine this value from information provided by the vCenter Client console or by using a third-party solution.