“As I was walking up the stair I met a man who wasn’t there. He wasn’t there again today.”

Was this man virtual? 

In the computer world, virtualization is a technique for hiding the physical computing resources from the way in which other systems, applications, or end users interact with those resources. This includes making a server or an operating system appear to function as multiple logical resources; or it can include making multiple physical resources (such as storage devices or servers) appear as a single logical resource.

The PCI Express protocol with I/O virtualization allows multiple operating systems running simultaneously within a single computer to share PCI Express devices. From the PCI-SIG website (http://www.pcisig.com/specifications/iov/)  These are grouped into three areas: 

• Address Translation Services (ATS): this specification provides a set of transactions for PCI Express components to exchange and use translated addresses in support of native I/O Virtualization.
• Single Root IOV: this specification provides native I/O Virtualization in existing PCI Express topologies where there is a single root complex.
• Multi-Root IOV: this specification builds on the Single Root IOV Specification to provide native I/O Virtualization in new topologies (such as blade servers) where multiple root complexes share a PCI Express hierarchy.

This functionality in the PCI Express protocol will enable network administrators virtualize or share peripherals and endpoints across different CPUs.

Any guesses on the author of the quote?