I often do data recovery jobs using
ddrescue or similar programs. The disk image is written sparsely, because often only parts of the disk is being imaged (using
ddrescue domain files and the like). However, on a heavily damaged disk,
ddrescue will skip hundreds of times, leading to a file with many fragments.
Until now I've been using an NTFS filesystem for storing the images, but I find that after heavy fragmentation the writes get bogged down (I believe NTFS rewrites the entire fragment metadata every time a new fragment is added).
Among the Linux filesystems is there one more optimized for fragmentation?