ZeroVM is efficient because it is made to virtualize applications, not machines. The runtime virtualizes only the server parts that do the actual work at hand – making it much faster. Today, the fastest virtual servers take at least two minutes to create, while ZeroVM takes less than 5 milliseconds – or 1/20,000th as long. ZeroVM is fast enough that you can put every request into its own mini-VM to spread horizontally.

Making things smaller, lighter and faster also provides greater security. ZeroVM is fast enough to isolate each individual user in a separate container, which delivers greater granularity of security and control.

Source: http://www.rackspace.com/blog/zerovm-smaller-lighter-faster/

Rackspace announced on Monday that it has acquired ZeroVM, a lightweight open-srouce hypervisor created by LifeStack

Source: http://www.thewhir.com/web-hosting-news/rackspace-acquires-open-source-hypervisor-zerovm