The Investigation And Improvement On Filesystem Check

Although the file system is becoming more and more robust, and the advanced technologies (such as logs, snapshots) more mature is applied to the file system, yet the file system check and repair tool is irreplaceable. Most of the current mainstream file systems have been equipped with appropriate detection and repair tool.This article analyze on FAT and NTFS file system and their check and repair tool CHKDSK and SCANDISK, UFS file system and its check and repair tool fsck, and HFS+ file system and its check and repair tool fsck.hfsplus, and particularly focus on the ExtX file system and its corresponding check and repair tool e2fsck.As for the currently existing defect of e2fsck three improvements are made : Firstly, in order to rectify its defect of causing false nodes parenthood while repairing the multi fan-in link, propose a new algorithm. Secondly, improve the original algorithm based on loop node bitmap, for e2fsck can not detect and repair the directory circulation problems in file system. But this improvement may occupy a large space and cause performance deficiencies, to make up for that we propose a speculation algorithm based on storing one of loop nodes, and This algorithm does not need to assign a bitmap to record the loop node information, but also can be optimized taking use of characteristics of the file system. Thirdly, in response to the block allocation policies and the security issues occurring when e2fsck is repairing the "dup block" of file system, we propose a adjacent block allocation policy based on dynamic staring block and a security strategy based on when the block copy block allocation strategy and security issues, based on dynamic block near the starting block allocation strategy and copy block information based on "dup block" information. Experimental results show that not only the improved e2fsck properly repare the node parenthood of multi fan-in link and file system'directory cycle, but also the algorithm based on storing one of loop nodes is apparently superior to the original algorithm while not reducing the overall performance of e2fsck .