USING ASYNCHRONOUS WRITES ON METADATA TO IMPROVE FILE SYSTEM PERFORMANCE

Due to the increasing gap between CPU and disk I/O speeds, the file sy stem is becoming the performance bottleneck in computer system design. How to improve file system performance is increasingly important. The re are two types of entities in a file system: data and metadata. Data mean the actual contents of files. Metadata include access control an d other descriptive information about files. Previous research indicat es that metadata writes account for 38 - 40% of disk I/O operations. T hese large numbers of control request I/Os are usually ignored in trad itional file system study, which concentrates only on file-level acces s patterns. We propose the design and implementation of a metadata-ord ering mechanism and its corresponding asynchronous write facility. Wit h such a facility, we can eliminate many synchronous metadata writes, and have the flexibility of choosing a better way to update these meta data modifications to disk asynchronously. Extensive performance evalu ation shows that substantial performance improvement can be achieved u nder various benchmarks. Some other tests are also used to demonstrate the benefits and behaviors of this approach.