Design and Implementation of File Layout in Redbud Parallel File System
File layout which manages the mapping relationship between logical offset of file and physical address of storage device is important for a file system.Redbud parallel file system(RFS)discards block-based file layout that distributed file systems implement in common,and carries out extent-based file layout which fits for sequential read and write on large files.Following the principle of meeting the minimum requirements which means the metadata server only returns the layout which meets the applications request on the clients can decrease the overhead on network transfers and improve the system performance of RFS.Moreover,RFS adopts the strategy of space continuous allocation and the strategy of extents real-time merger during file layout operating that can speed up metadata operations.We compared the performance of RFS with that of EXT3 and NFS by sequential and random reading and writing a 16GB file.The throughput of RFS gets 47.5% and 51.6% higher than that of NFS on random reading and writing,while it gets 65.6% and 75.1% higher on sequential reading and writing.The throughput of RFS also gets a little higher than that of EXT3 on sequential and random reading,while it gets 21.2% and 15.4% higher on sequential and random writing.The total throughput of RFS grows liner till the limitation of the test environment about 200MB/s.Test results show that Redbud parallel file system based on extent-based layout can provide high performance.