This is the review for the paper entitled “A Fast File System for Unix” by Marshall Kirk McKusick et. al. of the Computer Systems Research Group of University of California, Berkeley, rewritten in 1984.
The paper discussed about their reimplementation of UNIX file system where they adapt the system to a wide range of peripheral and processor characteristics. The new implementation of the system is tested to have ten times faster file access rate compared to the traditional UNIX file system. Several improvements on the file system were also discussed such as advisory locks on files, filename extension across file systems, ability to use long file names, and administrative control of resource usage.
The two major contributions of this paper are the modifications in the file system organization.
The first modification is on the storage utilization. The study optimized the storage utilization by increasing the block size. Through this bigger file can be transferred in a single disk transaction, thereby greatly increasing the throughput. However, Unix file system is composed of many small files, therefore large block size increases the space wasted. To resolve this issue. A single block is further partitioned into one or more addressable fragment. Since these fragments are addressable, multiple small files can reside on one data block.
The second modification is on the file system reparameterization. This modification is essential to the perform an optimal configuration-dependent block allocations. Each file system used are parameterized and adapted to the type of disk where it is placed. The parameters used are the speed of the processor, the hardware support for mass storage transfers, and the characteristics of the mass storage devices.
Although this paper significantly improved the data transfer, the time to read and write the file is almost similar to the reading rate of the older file system. The writing rate of the new file system is 50% slower than the older file system, because the kernel has to do twice as many disk allocations per second.