Running Xen.pdf - Mailing List

Virtual machine monitors also provide a uniform interface to the hardware. This uniform interface shields guest
systems from some lower level details of the physical computing resources and provides portability, which is
another key benefit of virtualization. In fact, many modern hypervisors allow guest systems to move from one
physical machine to another without interruption. Guest system configurations can easily be developed on one
machine and then deployed on many systems. This eases the job of managing or deploying software on a
collection of machines with different hardware characteristics. Guest systems can even migrate from one
physical computer to another while running. Xen calls this live migration. Some benefits of virtualization are as
follows.
Debugging operating systems is time consuming and requires exceptionally skilled programming.
Virtualization can ease the burden by allowing a developer to test new operating systems as a guest on a
more stable host. This technique has been used for many years and has proven effective. Similarly,
security researchers can create guest operating systems that are isolated from one another as well as the
host. Such guests allow researchers to study the effects of worms, Trojans, and viruses, without affecting
the host system. These isolated guests are colloquially referred to as being "sandboxed." Sandboxed
guests can also be used to test updates or cutting-edge software before applying them to production
systems.
Another benefit of virtualization is the ability to recover quickly from software problems caused by
deliberate malicious attacks or accidental malfunctions. By maintaining a copy of a stable guest image,
recovering from an attack can be as simple as rolling back to this trusted saved point.
Virtualization can provide higher availability by relocating guests when a server machine is inoperable.
Server environments can have many physical machines, each running a number of guest systems. Guest
systems can be moved seamlessly between physical machines to balance the load dynamically, thus using
the aggregate resources most efficiently. Many enterprise customers have enjoyed these benefits on
exotic hardware platforms for many years. Xen now provides these advantages to a wider audience.
Other benefits of virtualization become especially clear in a server environment. One example is the ability
to consolidate many services on one physical machine while still allowing each service to be administered
independently. In a multihosting environment, a service provider may run guest systems belonging to
many different individuals or businesses on the same physical machine. Each entity could have its own