Sprite (operating System) - Early Work

Early Work

Early work on Sprite was based on the idea of making the operating system more "network aware", and thereby at the same time make it invisible to the user. The primary area of work was the building of a new network file system which made heavy use of local client-side caching in order to improve performance. After opening the file and some initial reads, the network was only used on-demand, and most user actions would occur against the cache. Similar utilities allowed remote devices to be mapped into the local computer's space, allowing for network printing and similar duties.

Many of the key Unix files were based on the network, including things like the password file. All machines in a network shared the root directory as well. Other common Unix utilities such as finger were re-written to make them network aware as well, listing all of the people logged on across the network. This made a Sprite network appear as if it were a single large time-sharing system, or a single-system image.

Another key addition to Sprite was process migration, which allowed programs to be moved between machines at any time. The system maintained a list of machines and their state, and would automatically move processes to idle machines to improve local performance. Processes could also be "evicted" from machines to improve their performance, causing the original starter to move it to another machine on the network, or take control of it locally again. Long tasks (like compiling the Sprite system) could appear very fast.