Which statement best describes memory ballooning in virtualization?

Which statement best describes memory ballooning in virtualization?

• A. Memory ballooning reallocates memory from idle virtual machines to active ones.
• B. Memory ballooning increases the memory allocation for all virtual machines automatically.
• C. Memory ballooning reduces CPU usage by balancing processing.
• D. Memory ballooning creates additional swap space on local disks.

Answer: (A)

Memory ballooning is a memory reclamation mechanism in virtualization. A balloon driver inside each guest OS can be inflated, which makes the guest allocate memory internally and forces the guest to release physical pages back to the hypervisor. The hypervisor can then reassign those freed pages to other VMs that need more RAM. In practice, this means memory is reallocated from idle or less-demanding VMs to active ones under memory pressure, helping the host stay within its RAM limits. It doesn’t automatically boost memory for all VMs, it isn’t about balancing CPU usage, and it doesn’t create swap space on disks—the latter would be a separate consequence only if overall memory pressure remains after ballooning.

Memory ballooning is a memory reclamation mechanism in virtualization. A balloon driver inside each guest OS can be inflated, which makes the guest allocate memory internally and forces the guest to release physical pages back to the hypervisor. The hypervisor can then reassign those freed pages to other VMs that need more RAM. In practice, this means memory is reallocated from idle or less-demanding VMs to active ones under memory pressure, helping the host stay within its RAM limits. It doesn’t automatically boost memory for all VMs, it isn’t about balancing CPU usage, and it doesn’t create swap space on disks—the latter would be a separate consequence only if overall memory pressure remains after ballooning.