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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 Arrival rate, service time, utilization Little's law Squared coefficient of variance Average residual time Response time and utilization 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: 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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