A reimplementation of the UNIX TM file system is described.The reimplementation provides substantially higher throughput rates by using more flexible allocation policies that allow better locality of reference and can be adapted to a wide range of peripheral and processor characteristics.The new file system clusters data that is sequentially accessed and provides two block sizes to allow fast access to large files while not wasting large amounts of space for small files.File access rates of up to ten times faster than the traditional UNIX file system are experienced.Long-needed enhancements to the programmers' interface are discussed.These include a mechanism to place advisory locks on files, extensions of the name space across file systems, the ability to use long file names, and provisions for administrative control of resource usage.

This paper discusses the modifications made to the UNIX operating system for the VAX-11/780 to convert it from a swap-based segmented system to a paging-based virtual memory system. Of particular interest is that the host machine architecture does not include page-referenced bits. We discuss considerations in the design of page-replacement and load-control policies for such an architecture, and outline current work in modeling the policies employed by the system. We describe our experience with the chosen algorithms based on benchmark-driven studies and production system use.