【摘要】：隨著技術(shù)的發(fā)展，，音視頻相關(guān)的應(yīng)用逐漸普及，類似行車記錄儀的便攜式多媒體存儲(chǔ)系統(tǒng)更多的深入人們的生活。便攜式嵌入式設(shè)備多使用SD卡、U盤等可移動(dòng)存儲(chǔ)設(shè)備，以方便與PC機(jī)交換數(shù)據(jù)。由于FAT文件系統(tǒng)在各個(gè)操作系統(tǒng)上良好的兼容性，目前大多數(shù)便攜式嵌入式設(shè)備均使用FAT文件系統(tǒng)來存儲(chǔ)數(shù)據(jù)。 但是，F(xiàn)AT文件系統(tǒng)在進(jìn)行音視頻多媒體存儲(chǔ)特別是多路并發(fā)存儲(chǔ)時(shí)，會(huì)產(chǎn)生嚴(yán)重的碎片，影響讀寫性能。多媒體文件通常具有很大數(shù)據(jù)量，容易形成文件碎片。在并發(fā)存儲(chǔ)情況下，順序查找空閑簇并分配的策略使得不同文件的數(shù)據(jù)簇交織存儲(chǔ)，惡化了文件碎片情況。FAT文件系統(tǒng)的另一不足是對(duì)FAT表的嚴(yán)重依賴，文件的讀寫過程中對(duì)FAT表頻繁訪問的IO開銷一定程度上影響了讀寫效率。 多媒體文件存儲(chǔ)與傳統(tǒng)文本存儲(chǔ)不同，它具有一次寫入多次讀取，順序訪問，大數(shù)據(jù)量等特點(diǎn)，而FAT文件系統(tǒng)作為一種通用文件系統(tǒng)并不能很好地適應(yīng)這些特點(diǎn)。本文將結(jié)合多媒體文件的存儲(chǔ)特性，在保持兼容性的前提下對(duì)FAT文件系統(tǒng)進(jìn)行改進(jìn)，使之更適合多媒體的存儲(chǔ)。改進(jìn)工作包含兩個(gè)方面，一方面是在內(nèi)存中建立FAT表的位圖索引完成空閑簇的搜索，以便減少系統(tǒng)IO負(fù)荷；另一方面是在位圖索引基礎(chǔ)上，提出一種基于簇組的可變大小塊分配機(jī)制，用于擴(kuò)展空閑塊分配單元大小。論文通過測(cè)試表明，以上改進(jìn)提升了FAT文件系統(tǒng)在多路并發(fā)存儲(chǔ)條件下對(duì)于大文件的讀寫性能。
[Abstract]:With the development of technology, the application of audio and video is becoming more and more popular, and the portable multimedia storage system similar to CarLog goes deeper into people's life. Portable embedded devices use SD card, U disk and other removable storage devices to facilitate the exchange of data with PC. Because of the good compatibility of FAT file system in various operating systems, most portable embedded devices use FAT file system to store data. However, in the audio and video multimedia storage, especially in the multi-channel concurrent storage, the fat file system will produce serious fragments, which will affect the performance of reading and writing. Multimedia files usually have a large amount of data, easy to form file fragments. In the case of concurrent storage, the strategy of searching idle clusters sequentially and allocating them makes the data clusters of different files interleaved and stored, which exacerbates the file fragmentation. Fat file system is heavily dependent on FAT tables. The IO overhead of frequent access to FAT tables in the process of reading and writing of files affects the efficiency of reading and writing to a certain extent. The multimedia file storage is different from the traditional text storage. It has the characteristics of one write multiple read, order access, large amount of data, etc. As a general file system, FAT file system can not adapt to these characteristics. In this paper, we will improve the FAT file system on the premise of keeping compatibility with the storage characteristics of multimedia files to make it more suitable for multimedia storage. The improvement includes two aspects: on the one hand, building the bitmap index of FAT table in memory to complete the search of free cluster, in order to reduce the system IO load; on the other hand, on the basis of bitmap index, A variable size block allocation mechanism based on cluster group is proposed to extend the size of free block allocation unit. The test results show that the above improvements can improve the read and write performance of FAT file system for large files under the condition of multi-channel concurrent storage.
【學(xué)位授予單位】：華中科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2013
【分類號(hào)】：TP333

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