Case Study: Design and Performance Evaluation of a Permanent File Archiving System
A common problem confronting many computer installations is the allocation of the limited on-line disk space to the insatiable user demand for this space. When disks become so saturated that the system can no longer function efficiently, some files must be removed. This paper deals with the problem of attempting to optimally select among all the files those which should remain on-line and those which should be archived (information written to tape but directory entry with tape number left on-line). A user access of an archived file automatically spins off a system job to retrieve the file from its tape. An algorithm for selecting files for archiving was designed on the basis of some system performance goals and hypotheses about permanent file usage. An archiving performance analysis program was run periodically to monitor the impact on system performance, the impact on system resources and the accuracy of file selection. Two areas in which archiving might degrade system performance are the following: long waits by interactive users for archived files to become available, and a steep rise in the number of weekly tape mounts due to archived files. An adverse effect of archiving on system resources would be felt if the number of directory entries for archived files or the number of tapes needed to hold archived files increased greatly. Improvements in file selection were studied by characterizing files that either were frequently archived or were never archived and rarely used. 9 figures.
- Research Organization:
- Brookhaven National Lab., Upton, NY (USA)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- EY-76-C-02-0016
- OSTI ID:
- 5823545
- Report Number(s):
- BNL-26635; CONF-791202-1
- Journal Information:
- Conference Proceedings: 1979, Computer Measurement Group, Conference: CMG X International Conference on Controlled Resource Management through Computer Performance Evaluation, Dallas, TX, USA, 4 Dec 1979
- Country of Publication:
- United States
- Language:
- English
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