Despite the fact that the basic idea behind orthogonal persistence is very simple, research groups are finding it extremely hard to develop scalable and efficient persistent stores. One of the major difficulties derives from the fact that persistence provides a fundamentally different model of computing from that supported by conventional operating systems. In this project we are investigating the requirements of an operating system to support persistence and propose to design and construct a new operating system, known as Grasshopper, which has explicit support for persistent systems. Development of KeyKOS ceased in 1990. A new operating system based on a single, flat virtual address space, orthogonal persistence, and a strong but unintrusive protection model.
All Opal threads execute with a single global address space.