
520 Large Scale and Big Data
multiple VMs at a physical host and the physical memory turns stressed, none of the
VMs can automatically help in freeing up memory. The hypervisor deals with the
situation by applying a reclamation technique. As its name suggests, a reclamation
technique attempts to reclaim inactive real memory pages at VMs and make them
available for the hypervisor upon experiencing a memory shortage. One popular
reclamation technique is the ballooning process incorporated in VMWare ESX [62].
In VMWare ESX, a balloon driver must be installed and enabled in each guest OS
as a pseudodevice driver. The balloon driver regularly polls ...