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.

Since the invention of the movable head disk, people have improved I/O performance by intelligent scheduling of disk accesses. We have applied these techniques to systems with large memories and potentially long disk queues. By viewing the entire buffer cache as a write buffer, we can improve disk bandwidth utilization by applying some traditional disk scheduling techniques. We have analyzed these techniques, which attempt to optimize head movement and guarantee fairness in response time, in the presence of long disk queues. We then propose two algorithms which take rotational latency into account, achieving disk bandwidth utilizations of nearly four times a simple first come first serve algorithm. One of these two algorithms, a weighted shortest total time first, is particularly applicable to a file server environment because it guarantees that all requests get to disk within a specified time window. 1.

power and toward disk drives of rapidly increasing density, but with disk performance increasing very slowly if at all. The implication of these trends is that at some point the processing power of computer systems will be limited by the throughput of the input/output (I/O) system. A solution to this problem, which is described and evaluated in this paper, is disk cache. The idea is to buffer recently used portions of the disk address space in electronic storage. Empirically, it is shown that a large (e.g., 80-90 percent) fraction of all I/O requests are captured by a cache of an 8-Mbyte order-of-magnitude size for our workload sample. This paper considers a number of design parameters for such a cache (called cache disk or disk cache), including those that can be examined experimentally (cache location, cache size, migration algorithms, block sizes, etc.) and others (access time, bandwidth, multipathing, technology, consistency, error recovery, etc.) for which we have no relevant data or experiments. Consideration is given to both caches located in the I/O system, as with the storage controller, and those located in the CPU main memory. Experimental results are based on extensive trace-driven simulations using traces taken from three large IBM or IBMcompatible mainframe data processing installations. We find that disk cache is a powerful means of extending the performance limits of high-end computer systems. Categories and Subject Descriptors: B.3 [Hardware]: Memory Structures-design styles; performance analysis and design aids; B.4 [Hardware]: Input/Output and Data Communications-input

Areimplementation 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.

His interests include operating systems, distributed systems, user interfaces, and computer-aided design. He and his students have developed several wideI).-used programs for computer-aided design, including Magic, Caesar, and Crystal. Ousterhout is now leading the development of Sprite, a network operating system for highperfon'r, an_e workstations. Ousterhout is a recipient of the ACM Grace Murray Hopper Award,

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 speed of I/O components is a major limitation of the speed of all other major components in today's computer systems. Motivated by this, we investigated several algorithms for efficient and intelligent organization of files on a hard disk. Total access time may be decreased if files with temporal locality also have spatial locality. Three intelligent methods based on file type, frequency, and transition probabilities information showed up to 60% savings of total I/O time over the naive placement of files. More computationally intensive hill climbing and genetic algorithms approaches did not outperform statistical methods. The experiments were run on a real and simulated hard drive in single and multiple user environments. Introduction The performance of computer systems has rapidly improved during the last 40 years. However, the speed of I/O components still lags behind the speed of all other major components in most computer systems. Since most of the I/O deals with transferring ...

This paper presents a introduction to the concept of persistent authenticated dictionaries. It describes the design of two such dictionaries, one based on red-black trees, and one based on skip lists. Finally, it presents measurements of an implementation of persistent authenticated skip lists compared to ephemeral (non-persistent) skip lists and red-black trees

We present the results of a variety of trace-driven simulations of disk cache design. Our traces come from a variety of mainframe timesharing and database systems in production use. We compute miss ratios, run lengths, traffic ratios, cache residency times, degree of memory pollution and other statistics for a variety of designs, varying block size, prefetching algorithm and write algorithm. We find that for this workload, sequential prefetching produces a significant (about 20%) but still limited improvement in the miss ratio, even using a powerful technique for detecting sequentiality. Copy-back writing decreased write traffic relative to write-through; periodic flushing of the dirty blocks increased write traffic only slightly compared to pure write-back, and then only for large cache sizes. Write-allocate had little effect compared to no-write-allocate. Block sizes of over a track don't appear to be useful. Limiting cache occupancy by a single processor transaction appears to have little effect. This study is unique in the variety and quality of the data used in the studies.