MARS: How is the percentage of File Disorder and Slack Space calculated.
A block is considered to be disordered if its logical order (by key value) in relation to adjacent blocks within the file does not match the physical order of those blocks.
To estimate disorder, MARS selects approximately 100 blocks from random positions within the file being analyzed. The entire file is not read to minimize resource consumption and to provide faster results. In our experience, sampling a small portion of the file provides a value with a margin of error of less than 5% in most cases. If you wish to read an entire file for detailed analysis, MARS includes a TACL-based tool, called MRA, which may be found in the MARS installation subvolume.
MARS performs its slack space analysis on the same 100 blocks randomly selected for File Disorder from the file.
MARS takes few milliseconds to access one block of data within a file, and it should take about few seconds to scan a file. This allows MARS to evaluate a large number of files within minimal delay and resource consumption.
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