A Trace-Driven Analysis of the UNIX 4.2BSD File System
CALIFORNIA UNIV BERKELEY DEPT OF ELECTRICAL ENGINEERING AND COMPUTER SCIENCES
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We analyzed the UNIX 4.2BSD file system by recording activity in trace files and writing programs to analyze the traces. The trace analysis shows that the average file system bandwidth needed per user is low a few hundred bytes per second. Most of the files accessed are short, are open a short time, and are accessed sequentially. Most new information is deleted or overwritten within a few minutes of its creation. We wrote a simulator that uses the traces to predict the performance of caches for disk blocks. The moderate-sized caches used in UNIX reduce disk traffic by about 50, but larger caches several megabytes can achieve much greater reductions, eliminating 90 or more of all disk traffic. With those large caches, large block sizes 16 kbytes or more result in the fewest disk accesses.
- Computer Programming and Software
- Computer Systems Management and Standards