The Design and Implementation of the 4.4BSD Operating System

Chapter 8Local Filestores

This chapter describes the organization and management of data on storage media. 4.4BSD provides three different filestore managers: the traditional Berkeley Fast Filesystem (FFS), the recently added Log-Structured Filesystem (LFS), and the Memory-based Filesystem (MFS) that uses much of the FFS code base. The FFS filestore was designed on the assumption that buffer caches would be small and thus that files would need to be read often. It tries to place files likely to be accessed together in the same general location on the disk. It is described in Section 8.2. The LFS filestore was designed for fast machines with large buffer caches. It assumes that writing data to disk is the bottleneck, and it tries to avoid seeking ...