Abstract
Small file accesses are still limited by disk head move-ment on modern disk drives with the high disk bandwidth. Small file performance can be improved by grouping and clustering, each of which places multiple files in a direc-tory and places blocks of the same file on disks contigu-ously. These schemes make it possible for file systems to use large data transfers in accessing small files, reducing disk accesses. However, as file systems become aged, disks become too fragmented to support the grouping and clus-tering of small files. This fragmentation makes it difficult for file systems to take advantage of large data transfers, increasing disk I/Os. To offer a solution to this problem, we describe a De-fragmented File System (DFS). By using data cached in memory, DFS relocates and clusters data blocks of small fragmented files in a dynamic manner. Be-sides, DFS clusters related small files in the same directory at contiguous disk locations. Measurements of DFS imple-mentation show that the techniques alleviate file fragmenta-tion significantly and, in particular, performance for small file reads exceeds that of a traditional file system by 78%.