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An Efficient Cleaning Scheme for File Defragmentation on Log-Structured File System
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  • Journal title : Journal of KIISE
  • Volume 43, Issue 6,  2016, pp.627-635
  • Publisher : Korean Institute of Information Scientists and Engineers
  • DOI : 10.5626/JOK.2016.43.6.627
 Title & Authors
An Efficient Cleaning Scheme for File Defragmentation on Log-Structured File System
Park, Jonggyu; Kang, Dong Hyun; Seo, Euiseong; Eom, Young Ik;
When many processes issue write operations alternately on Log-structured File System (LFS), the created files can be fragmented on the file system layer although LFS sequentially allocates new blocks of each process. Unfortunately, this file fragmentation degrades read performance because it increases the number of block I/Os. Additionally, read-ahead operations which increase the number of data to request at a time exacerbates the performance degradation. In this paper, we suggest a new cleaning method on LFS that minimizes file fragmentation. During a cleaning process of LFS, our method sorts valid data blocks by inode numbers before copying the valid blocks to a new segment. This sorting re-locates fragmented blocks contiguously. Our cleaning method experimentally eliminates 60% of file fragmentation as compared to file fragmentation before cleaning. Consequently, our cleaning method improves sequential read throughput by 21% when read-ahead is applied.
Log-structured file system;file fragmentation;flash memory;read-ahead;
 Cited by
Y. Kang, K. Han, and D. Shin, "Improving the Performance of Log-Structured File Systems Using Logical Copy Technique," Proc. of the KIISE Korea Computer Congress, pp. 1258-1260, 2008. (in Korean)

C. Min, K. Kim, H. Cho, S. Lee, and Y. Eom, "SFS: Random Write Considered Harmful in Solid State Drives," Proc. of USENIX Conference on File and Storage Technologies, pp. 12, 2012.

J. Engel and R. Mertens, "LogFS-finally a Scalable Flash File System," Proc. of International Linux System Technology Conference, pp. 135-142, 2005.

A. Schierl, G. Schellhom, D. Haneberg, and W. Reif, "Abstract Specification of the UBIFS File System for Flash Memory," Proc. of International Symposium on Formal Methods, pp. 190-206, 2009.

S. Lim and K. Park, "An Efficient NAND Flash File System for Flash Memory Storage," IEEE Transactions on Computers, Vol. 55, No. 7, pp. 906-912, 2006. crossref(new window)

M. Rosenblum and J. K. Ousterhout, "The Design and Implementation of a Log-Structured File System," ACM Transactions on Computer Systems, Vol. 10, No. 1, pp. 26-52, 1992. crossref(new window)

L. Robert, Linux Kernel Development, 3rd edition, Pearson Education, 2010.

V. Steve, C. Frost, and E. Kohler, "Reducing Seek Overhead with Application-Directed Prefetching," Proc. of USENIX Annual Technical Conference, pp. 24, 2009.

M. Kaczmarczyk, M. Barczynski, W. Kilian, and C. Dubnicki, "Reducing Impact of Data Fragmentation Caused by In-line Deduplication," Proc. of ACM International Systems and Storage Conference, pp. 15, 2012.

K. A. Smith and M. I. Seltzer, "File System Aging-Increasing the Relevance of File System Benchmarks," ACM SIGMETRICS Performance Evaluation Review, Vol. 25, No. 1, pp. 203-213, 1997. crossref(new window)

R. Mendel and J. K. Ousterhout, "The LFS Storage Manager," Proc. of USENIX Summer 1990 Technical Conference, pp. 315-324, 1990.

T. Blackwell, J. Harris, and M. I. Seltzer, "Heuristic Cleaning Algorithms in Log-Structured File Systems," Proc. of USENIX 1995 Technical Conference, pp. 277-288, 1995.

C. Lee, D. Sim, J. Hwang, and S. Cho, "F2FS: A New File System for Flash Storage," Proc. of USENIX Conference on File and Storage Technologies, pp. 273-286, 2015.

W. D. Norcott and D. Cappas. (2016, Jan 23). IOzone filesystem benchmark [Online]. Available: (downloaded 2016, Feb. 12)