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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;
 
 Abstract
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.
 Keywords
Log-structured file system;file fragmentation;flash memory;read-ahead;
 Language
Korean
 Cited by
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