A reimplementation of the UNIX 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.

Modern high-end disk arrays often have several gigabytes of cache RAM. Unfortunately, most array caches use management policies which duplicate the same data blocks at both the client and array levels of the cache hierarchy: they are inclusive. Thus, the aggregate cache behaves as if it was only as big as the larger of the client and array caches, instead of as large as the sum of the two. Inclusiveness is wasteful: cache RAM is expensive. We explore the benefits of a simple scheme to achieve exclusive caching, in which a data block is cached at either a client or the disk array, but not both. Exclusiveness helps to create the effect of a single, large unified cache. We introduce a DEMOTE operation to transfer data ejected from the client to the array, and explore its effectiveness with simulation studies. We quantify the benefits and overheads of demotions across both synthetic and real-life workloads. The results show that we can obtain useful -- sometimes substantial -- speedups. During our investigations, we also developed some new cache-insertion algorithms that show promise for multi-client systems, and report on some of their properties.

This paper describes the motivations for memory-based filesystems. It compares techniques used to implement them and describes the drawbacks of using dedicated memory to support such filesystems. To avoid the drawbacks of using dedicated memory, it discusses building a simple memory-based filesystem in pageable memory. It details the performance characteristics of this filesystem and concludes with areas for future work. 1.

A reimplementation of the UNIX 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. Revised February 18, 1984 CR Categories and Subject Descriptors: D.4.3 [Operating Systems]: File Systems Management - file organization, directory s...

The memory on a computer is organized into a hierarchy of storage [Smith 1981]. This storage ranges from small and fast to slow and huge. Figure 1 shows a typical hierarchy. It is composed of two main parts: the primary store and the secondary store. This paper is concerned with the secondary part of the storage. Many types of hardware are used to support secondary storage. These devices include magnetic disks, magneto-optical disks, compact disk-read-only memory (CD-ROM) disks, and various sorts of tape oriented devices.