Research On Journal File System For Object-Based Storage

The file system is an important part of a modern operating system. It is crucial that the file system is access speed, I/O efficiency and reliable. As the main file system of current Linux OS, Ext2 file system has some drawbacks in processing the big files and giant bibliographic structures. It is also still possible that computers shut down unexpectedly as the result of hardware or software failures or because of power outages. When this happens, Ext2 file system has to scan through the whole file system content, to find inconsistencies. These problems are determined by Ext2's internal structure. The Ext2 file system was designed for the middle or small files, it adopted traditional linear list and multilevel pointers index structure to organize data stactically; it is devoid of a mechanism to speed up the lengthy recovery process after an unclean system shutdown.In order to change these situations, implement the rapid access to files, strengthen the support and management for lage-scale file system, we bring forward and implement a file system based on exntent and organized by B+ tree (Object-Based Journal File System, OSJFS), which can expand the functions of file system in several aspects: firstly, using B+ tree to organize the large file datum, free blocks and directory entries. By B+ tree indexing structure, the access speed of large files and directory is raised obviously and the address ability is also expanded; the traditional block allocation policy is replaced by the extent allocation policy, which can reduce the I/O times in allocation, keep the file datum stored spatially, lessen the external fragmention and improve the efficiency of access.Secondly, analyzing the features of popular journaling file systems, we choose the Ext3 file system as the referenced prototype with an eye to the feature of OSD; to the small file, we can store the file datum directly in the inline data field of the inode, which can improve the I/O performance of small file and lessen internal fragmention.Finally, we analyse the performance of OSJFS with the benchmarks.