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Definition of Terms Talking about blocking data into chunks of fixed size one typically uses the terms of internal and external fragmentation. • Internal Fragmentation: This is the (average) loss of space when blocking data into blocks of fixed size due to the ends of files not filling a whole block. Of course you want to keep this number small not wasting much of memory space eg. by using fragments (FFS) or putting tails of files together (ReiserFS). In my simulations I calculate the average internal fragmentation by dividing the number of bytes that are on disk per file or per partition disk by the number of theoretically usable bytes which is the number of blocks used times the block size. One can argue, that a log file on disk (or metadata in general) will automatically enlarge internal fragmentation as its space cannot be used for user data. I am not accounting that for internal fragmentation. • External Fragmentation: This is the (average) loss of performance when the physical block layout on disk is not optimized for the disc mechanics such as that for many files the blocks belonging to one file are scattered around the whole disc.
Approximate Word count = 757
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