Sprite operating system
Encyclopedia
Sprite was an experimental Unix-like
distributed operating system
developed at the University of California, Berkeley
by John Ousterhout
's research group between 1984 and 1992. Its notable features included support for single system image on computer clusters and for the introduction of the log-structured filesystem. The Tcl
scripting language also originated in this project.
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
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.
(LFS), development of which continued until about 1992. LFS dramatically increases the performance of file writes at the expense of read performance. Under Sprite, this tradeoff is particularly useful because most read access was cached anyway—that is, Sprite systems would typically perform fewer reads than a normal Unix system. LFS-like systems also allow for much easier crash recovery, which became a major focus of the project during this period. Additional experimentation on striped file systems, both striped across different machines as well as clusters of drives, continued until about 1994.
system, and suffered the same sort of problems as other Unix
es in terms of development complexity, becoming increasingly difficult to develop as more functionality was added. By the 1990s it was suffering and the small team supporting the project was simply not able to keep up with the rapid changes in Unix taking place during this time. The project was slowly shut down by 1994.
Unix-like
A Unix-like operating system is one that behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification....
distributed operating system
Distributed operating system
A distributed operating system is the logical aggregation of operating system software over a collection of independent, networked, communicating, and spatially disseminated computational nodes. Individual system nodes each hold a discrete software subset of the global aggregate operating system...
developed at the University of California, Berkeley
University of California, Berkeley
The University of California, Berkeley , is a teaching and research university established in 1868 and located in Berkeley, California, USA...
by John Ousterhout
John Ousterhout
John Kenneth Ousterhout is the chairman of Electric Cloud, Inc. and a professor of computer science at Stanford University. He founded Electric Cloud with John Graham-Cumming. Ousterhout previously was a professor of computer science at University of California, Berkeley where he created the Tcl...
's research group between 1984 and 1992. Its notable features included support for single system image on computer clusters and for the introduction of the log-structured filesystem. The Tcl
Tcl
Tcl is a scripting language created by John Ousterhout. Originally "born out of frustration", according to the author, with programmers devising their own languages intended to be embedded into applications, Tcl gained acceptance on its own...
scripting language also originated in this project.
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-sharingTime-sharing
Time-sharing is the sharing of a computing resource among many users by means of multiprogramming and multi-tasking. Its introduction in the 1960s, and emergence as the prominent model of computing in the 1970s, represents a major technological shift in the history of computing.By allowing a large...
system, or a single-system image
Single-system image
In distributed computing, a single system image cluster is a cluster of machines that appears to be one single system. The concept is often considered synonymous with that of a distributed operating system, but a single image may be presented for more limited purposes, just job scheduling for...
.
Another key addition to Sprite was process migration
Process migration
Process migration is when processes in computer clusters are able to move from machine to machine. Process migration is implemented in, among others, OpenMosix....
, 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
Compiler
A compiler is a computer program that transforms source code written in a programming language into another computer language...
the Sprite system) could appear very fast.
Further development
Work on the "early" Sprite outlined above ended around 1987, but was improved during the next year. Starting in 1990 Sprite was used as the basis for development of the first log-structured file systemLog-structured file system
A log-structured filesystem is a file system design first proposed in 1988 by John K. Ousterhout and Fred Douglis. Designed for high write throughput, all updates to data and metadata are written sequentially to a continuous stream, called a log...
(LFS), development of which continued until about 1992. LFS dramatically increases the performance of file writes at the expense of read performance. Under Sprite, this tradeoff is particularly useful because most read access was cached anyway—that is, Sprite systems would typically perform fewer reads than a normal Unix system. LFS-like systems also allow for much easier crash recovery, which became a major focus of the project during this period. Additional experimentation on striped file systems, both striped across different machines as well as clusters of drives, continued until about 1994.
Discontinuation
Sprite was not a microkernelMicrokernel
In computer science, a microkernel is the near-minimum amount of software that can provide the mechanisms needed to implement an operating system . These mechanisms include low-level address space management, thread management, and inter-process communication...
system, and suffered the same sort of problems as other Unix
Unix
Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...
es in terms of development complexity, becoming increasingly difficult to develop as more functionality was added. By the 1990s it was suffering and the small team supporting the project was simply not able to keep up with the rapid changes in Unix taking place during this time. The project was slowly shut down by 1994.