
505Virtualizing Resources for the Cloud
As opposed to a single system component, when virtualization is applied to an
entire machine, it provides what is known as a virtual machine (VM). Specically,
a full set of hardware resources, including processors, memory, and I/O devices will
be virtualized to provide the VM. As shown in Figure 16.8, an underlying hardware
machine is usually referred to as host and an OS running on a VM is denoted as
guest OS. A VM can only run at a single host at a time. As compared with a host,
a VM can have resources different in quantity and in type. For instance, a VM can
obtain more processors than what a host off ...