关键词: 航天器, BLOF, 文件系统, 二元组, 索引

Abstract: Flash equipment is used as the storage medium on spacecraft, and file system is needed to manage the storage equipment. In the space embedded system, the scale of data storage is becoming larger and larger, and the amount of data generated by the acquisition task will reach the level of TB. For the sake of security, the memory capacity of spacecraft embedded system is limited, and the real time requirement is very high. Common embedded system is different from aerospace embedded system in memory capacity and real time requirements, so it is not suitable for aerospace embedded system. In order to meet special requirements of limited spacecraft system resources, and to resolve the problem that the space occupied by file index structure in memory increases linearly with the amount of file data in YAFFS2 which is a commonly used embedded file system, a new index method called BLOF(low overhead and fast file management based on binary group) is proposed in which continuous FLASH pages are indexed uniformly by introducing binary group structure based on B+ tree, and the file read and file write algorithms according to the index structure are designed. So that the file system can implements fast file reading and writing, and low memory footprint. The experimental results show that compared with the YAFFS2 index method, BLOF is more effective in the following cases: 1) when the number of FLASH pages for storing file data reaches an average of six or more consecutive pages, BLOF takes less memory footprint than YAFFS2, and maximum saving is 55.55%; 2) when the file size is greater than 512KB, the file reading and writing time of the BLOF method is always less than that of YAFFS2, and the value of YAFFS2 file writing time minus BLOF file writing time increases linearly with the file size. BLOF method is more suitable for the situation where the file data is large and stored in a large number of continuous pages.

Key words: spacecraft, BLOF, file system, binary group, index