Log File Service Exploiting Write-Once Storage

摘要

The authors propose that logs should be the fundamental data abstraction provided by an append-only storage medium, with log files being made available to applications as an operating system service. The authors describe the design of the 'Clio' logging service, and show how this design provides efficient access to large numbers of independent log files, with low space overhead, despite the restriction on possible data structures imposed by the use of append-only storage. An implementation of Clio for the V-System, using a write-once optical disk for permanent storage, provides measurements in support of these results. Finally, the authors show how an application may be built upon a logging service such as Clio, with one or more log files providing the application's only form of persistent storage. The authors describe both the benefits and the drawbacks of this approach, and, in particular, describe how a general file system can be structured in this manner.