Paravirtualization

Paravirtualization is State of the Art Virtualization
Paravirtualization, created by the founders of the Xen® hypervisor project, fundamentally altered the way virtualization technology was architected. With this technology the virtual servers and hypervisor co-operate to achieve very high performance for I/O, CPU, and memory virtualization. The Xen hypervisor appears to the virtualized server as an idealized hardware abstraction layer that offers superb performance. In fact, the Xen hypervisor offers a smaller code base, greater security, and up to 10 times less overhead then alternative virtualization approaches

Leverages Hardware Virtualization
In addition, the Xen hypervisor uniquely takes advantage of hardware virtualization support from Intel® and AMD® processors to enable virtualized guests to run natively on the hardware while still achieving very high performance I/O. With alternative approaches, the hypervisor must binary patch running guests to prevent them from interacting with the hardware, resulting in high performance overhead, stability, and security risks. Moreover, this approach results in significant I/O performance impact.

Paravirtualization Provides Superior Performance
Paravirtualization requires a tiny hypervisor code base (the Xen hypervisor is under 50 KLOC) that results in extremely low performance overhead, typically in the range of 0.1% to 3.5% for industry standard performance benchmarks. It also leverages all of the native Linux device drivers and therefore supports an extremely diverse set of drivers. Xen’s paravirtualized drivers run outside the core hypervisor, where they implement policy for resource sharing between multiple guests, providing fine-grained partitioning of I/O between multiple virtual servers. Another benefit of this approach is that drivers run at a lower protection level than Xen, making the hypervisor impervious to driver failure.