Compressed Embedded File System: Design And Implementation

In embedded Linux systems, storage device is always shortage. Sometimes it is necessary to use a compressed file system. The two popular compressed file systems use gzip as their compression algorithm. However, gzip is not always the best algorithm to use.Five compression algorithms are compared and analyzed. Data about their decompression speed and compression ratio is given. Result shows that in most compression algorithms, the decompression speed is not affected by the compression arguments. The algorithms most fit for compressed file systems are selected according to the results of the experiment.The benefit of applying different compression algorithms to different files in the file system is discussed. A file system using multiple compression algorithms is designed, which is named as Compressed Embedded File System (CEFS).Based on the method used in cramfs, the storage structure of cefs is implemented, which can significantly save space. Methods to analyze the access to files are discussed. Methods of selecting compression algorithms are given. A compression configuration file based on md5 digests is designed.The design of cefs is detailed in this paper. Results of experiments are given.