You have probably encountered that. An external hard drive that after many switch offs and switch ons (without safely unmounted it) refuses to mount with an error like this :
“Error mounting: mount exited with exit code 13: $MFTMirr does not match $MFT (record 0).”
The solution to that would be to run chkdisk on a Windows machine, but if you are like me (totally free of MS) then you are out of luck.. or not? Not! because you can use a handy set of tools that come be default in Fedora (namely the ntfsfix tool) that can help you repair the damaged NTFS partition. Just make sure you run it as root, appending the name of the drive (e.g. /dev/sdc1) that has the problem.
Remember that applies only for external disks formatted as NTFS and unable to be mounted due to trouble caused by abruptly switching them on and off.
More info can be found here