The architecture of Ra: a kernel for Clouds

Ra is a native, minimal kernel for the Clouds distributed operating system. Ra is a successor to the prototype Clouds kernel and reflects lessons learned from the earlier implementation effort. Ra supports the same object-thread model as the original Clouds kernel as a special case and introduces extensibility as a major goal. Ra provides three primitives, namely segments, virtual spaces, and lightweight processes called isibas, which can be composed in various ways to construct components of the Clouds operating system. The architecture and organization of Ra and details of its implementation are described. The authors describe the implementation of several Clouds components such as objects and threads using Ra primitives to demonstrate the versatility and power of the Ra kernel. Ra supports plug-in system objects that allow system services to be introduced and removed dynamically. Ra has been implemented in C++ and is running on Sun-3 workstations.<>