Hello, I'm try to recover data using dd_recovery, everything seems to be ok, but after 40GB backup, dd_rescue still wrote I/O error for two days, so I'm terminate dd_rescue and now i can't mount my image by "mount -o loop /home/user/diskimage.img /mnt/diskimg/ -t ntfs and "mount" command wrote the ntfs signature is missing. Is there any hope to mount image and retrieve my data back?

Thank for reply and sory for beginer's question.

Here are a couple of brief comments. Other people may have different opinions:

You should not expect to be able to successfully mount an incomplete clone. Occasionally it is possible (depending on exactly what filesystem metadata is missing), but don't bet on being able to do so. In any case, mounting a clone has risks, so mitigation is recommended (e.g. copy the clone first). Currently you're likely limited to recovery attempts from that image, rather than mounting it. Hopefully whatever instructions you are following, will explain this situation.

You haven't given much detail of exactly what you did and why, so I can't add much more (and personally I choose GNU ddrescue instead of dd_rescue anyway). If dd_rescue didn't try to read every block (check its logfile, if you used it), then you may want to consider an alternative approach.