lec31 - Problem: file's blocks get distributed all over the...

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LECTURE - 31
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Lecture Outline ± Some queuing theory ± UNIX Fast File System ± ± Scribe for today?
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I/O Performance ± Producer-Server Model ± Throughput vs. Response Time ± Response time and think time ± Queuing theory ² Arrival rate, service time, utilization ² Little's law ² Squared coefficient of variance ² Average residual time ² Response time and utilization ² M/G/1 and M/M/1 models
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UNIX's Old File System ± Superblock ± Free-list ± Directory: special file – has pointer to file's inode ± Inodes have: ² Direct points, singly indirect pointers, doubly indirect, and triply indirect pointers ±
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Unformatted text preview: Problem: file's blocks get distributed all over the disk, deteriorating performance ± Also, block size: 512 bytes (poor performance) UNIX Fast File System (FFS) ± Cylinder groups are defined ± Inodes are close to data blocks ± Block size: 4096 bytes ² But, poor disk usage (close to 50% wasted) ± Idea: fragment blocks ² But only last block of file is allowed to be fragmented ± All files of a directory are preferably in same cylinder group ± Other enhancements: long file names, file locking, symbolic links, rename, quota...
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This note was uploaded on 07/14/2011 for the course CS 422 taught by Professor Hogakoi during the Spring '10 term at IIT Kanpur.

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lec31 - Problem: file's blocks get distributed all over the...

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