Research Andapplication Of FAT File System For Multimedia Storage

With the development of technology, audio and video related applications arebecoming more common, portable multimedia storage system like vehicle recorderbecomes more and more important in people’s life. In order to exchange data with PC,embedded devices usually use SD cards, U disks or other removable storage devices.Because of the excellent compatibility of FAT file system in various operating systems,most portable embedded devices use it as their file system.However, the FAT file system will cause severe fragmentation when used to storemultimedia files, especially in concurrent storage environment, affecting read and writeperformance. In concurrency storage case, free cluster allocation strategy makes the dataclusters of different multimedia files interleaving, deteriorating file fragmentation.Another deficiency of FAT file system is its heavily dependence on FAT table, the IO offrequently accessing to FAT affects read-write efficiency.Multimedia files are usually written once but read many times, accessed in sequenceand of a large amount of data. However, the FAT file system as a general-purpose filesystem is not well adapted to these characteristics. In this thesis, some improvements aremade to make FAT file system more suitable for multimedia storage. Firstly, bitmapindex is established in memory for FAT table to accelerate the search of free clusters.Secondly, a variable size block allocation mechanism based on the cluster group isintroduced for the expansion of the free block allocation unit size. Tests show aboveimprovements can enhance read and write performance of the FAT file system for theconcurrent storage of large files.