The virtio-balloon driver allows guests to express to the hypervisor how much memory they require. The balloon driver allows the host to efficiently allocate and memory to the guest and allow free memory to be allocated to other guests and processes. Guests using the balloon driver can mark sections of the guests RAM as not in use (balloon inflation). The hypervisor can free the memory and use the memory for other host processes or other guests on that host. When the guest requires the freed memory again, the hypervisor can reallocate RAM to the guest (balloon deflation).

This includes:
- Memory balloon optimization (Users can now enable virtio-balloon for memory optimization on clusters. All virtual machines on cluster level 3.2 and higher includes a balloon device, unless specifically removed. When memory balloon optimization is set, MoM will start ballooning to allow memory overcommitment, with the limitation of the guaranteed memory size on each virtual machine.
- Ballooning error messages (When ballooning is enabled for a cluster, appropriate messages now appear in the Events tab)