In virtualization, which memory technique allows more memory to be allocated to VMs than physical RAM would allow?

• A. Memory Bursting
• B. Ballooning
• C. Swap
• D. Transparent Page Sharing

Answer: (A)

Memory overcommitment is the idea of giving VMs more virtual RAM than physical RAM available, by reclaiming memory from VMs when needed. The mechanism that makes this practical is memory ballooning. A balloon driver inside each VM can "claim" some of the VM’s memory, which the hypervisor can then reallocate to other VMs when pressure arises. This lets the host present the illusion of more memory to all VMs than the physical host actually has, improving consolidation opportunities.

Swapping moves memory to disk and is a fallback that can degrade performance, not the primary enabler of overcommitment. Transparent Page Sharing reduces the total memory footprint by deduplicating identical pages, but it doesn’t increase the amount of memory that can be allocated across all VMs. Memory bursting isn’t a standard term used for this concept.