Many workloads present opportunities for sharing memory across virtual machines.
For example, several virtual machines might be running instances of the same guest operating system, have the same applications or components loaded, or contain common data. ESXi systems use a proprietary page-sharing technique to securely eliminate redundant copies of memory pages.
With memory sharing, a workload consisting of multiple virtual machines often consumes less memory than it would when running on physical machines. As a result, the system can efficiently support higher levels of overcommitment.
The amount of memory saved by memory sharing depends on workload characteristics. A workload of many nearly identical virtual machines might free up more than thirty percent of memory, while a more diverse workload might result in savings of less than five percent of memory.