VMware has perfected some powerful techniques by which RAM can be managed and optimized on a vSphere host in order to provide additional scalability on a per-host basis and to keep a host operating a peak levels.
- VMware Oversubscription/Overcommit. Allows administrators to assign more aggregate RAM to virtual machines than is actually physically available in the server.
- Transparent Page Sharing.This is basically a deduplication method applied to RAM rather than storage
- Guest Ballooning.When VMware Tools is installed inside a virtual machine, along with everything else is a memory balloon process. The guest operating system can swap processes out to help free up memory that is then assigned to the balloon.
- Memory compression attempts to fit multiple pages of RAM into a smaller number of pages in order to postpone for as long as possible the need for the hypervisor to swap to disk. Disk swapping is expensive in terms of performance.