On "A Fast File System for UNIX"

Post date: Nov 23, 2012 12:29:28 PM

This paper discusses improvements on the file system used for UNIX-based operating systems.

The paper claims that the enhancements in [1] for PDP-11 suits well due to an elegant file system facility for the computer, however, is not flexible and stable for other file system implementation. This is observed when these enhancements were employed for VAX-11 computers. Since the techniques in [1] are well-understood, not inherently slow, and allows for abstraction from how applications view file accesses, only the implementation of the file systems are enhanced. Some of the characteristics for the improved file system implementation are (a) division of file system blocks to one or more fragments to minimize waste of space, (b) file system depends on selected processor information and mass storage information for block allocation, (c) creation of layout policies to decide on optimal placement for directories and files. Other enhancements in the file system implementation include (1) use of long file names, (2) file locking mechanism, (3) introduction of symbolic links to enable referencing of inodes across physical file systems, (4) allowing data files and directories to be renamed and (5) placement of quota for the amount of file system resource a user can obtain.

As can be observed, the contribution of the paper is the enhancements in the file system implementation which is used to make the file system intelligent in obtaining optimal placement of files and directories. This is not prioritized in the previous implementation of the file system. This results to maximization of throughput while maintaining the elegance of the proposed implementation in [1], with tradeoff of overhead resource for the additional computation. This may result to performance degradation as the number of processed files increase. Techniques to minimization this additional computation may be explored to further improve the performance of the system.

[1] D. Ritchie, K. Thompson. The UNIX Time-sharing System. Communications of the ACM, 17, 7, 365-375 (1974)