UGC NET CSE | December 2007 | Part 2 | Question: 25

Question

The performance of a file system depends upon the cache hit rate. If it takes $1$ msec to satisfy a request from the cache but $10$ msec to satisfy a request if a disk read is needed, then the mean time (ms) required for a hit rate $’h’$ is given by :

• A. $1$
• B. $h+10(1-h)$
• C. $(1-h)+10h$
• D. $10$

Answer 1

option B is correct.Since the hit ratio is h, so the miss ratio is (1- h) and time for cache access is 1 ms and that of hard disk is 10ms ,so the avaerage access time is give by = hit ratio* cache access time + (1-hit ratio)*disk access time =h*1+(1-h)*10=h+(1-h)10 which is the option B.