e4defrag vs O&O Defrag

e4defrag is a Linux utility for defragmenting extent-based files on ext4 filesystems. It accepts an individual file, a directory and its files, or a device mounted as ext4. The utility aims to place targeted data in more contiguous blocks, which the manual says can improve file access speed. Its -c option reports current and ideal fragmentation counts and a fragmentation score without making changes; the score appears only when the check runs as root. With -v, it prints error messages and each file’s fragmentation count before and after defragmentation. e4defrag checks for ext4 and reports an error for other filesystem types. It does not support swap files, files in lost+found, or files allocated in indirect blocks. A target device or mount point excludes files belonging to another device’s mount point, and fragmented or insufficient free space can prevent improvement. The manual says it is safe to run while another application uses a file, though shared memory and disk bandwidth can slow both. It is free at free.

O&O Defrag has no write-up on Specifiction yet; its figures are above.