HighLight: a file system for tertiary storage

HighLight, a file system combining secondary disk storage and tertiary robotic storage that is being developed as part of the Sequoia 200 Project, is described. HighLight is an extension of the 4.4BSD log-structured file system (LFS), which provides hierarchical storage management without requiring any special support from applications. The authors present HighLight's design and various policies for automatic migration of file data between the hierarchy levels. The performance of HighLight was compared with that of the 4.4BSD LFS implementation. The initial results indicate that HighLight's performance is comparable to that of 4.4BSD LFS for disk-resident data, and the overhead associated with accessing data from the tertiary cache is negligible