I'm currently in the business of recovering data from a damaged---and dying---hard-drive (check this question for background info). The damaged hard-drive is 250GB, and I intend to use dd or ddrescue to clone what is left of the disk (as suggested in How to clone a NTFS partition (WinXP) from a damaged disk to a new one?).

For such a cloning operation, is a healthy 250GB external hard-drive sufficient? Or must the drive be bigger than that (say, 320GB)? And if the damaged source disk is indeed one sector larger than the healthy destination disk, how exactly could this impact/confuse dd or ddrescue?

In the end I got the new disk and it is sector for sector the same size as the damaged disk: 488397168 sectors.

2 Answers 2


Same size should be fine, however, I believe dd copies sector for sector, so when the source disk is only by one sector larger I think you will run into problems. Better just get a larger HDD. You can use Gparted to enlarge the original partition to fit even more files.


link above gives some more information about dd, drive sizes and recovering data from an old HDD. The suggestion of using clonezilla speaks most to me, since clonezilla is meant for copying HDD and has a fine working ncurses interface.

Good luck!

  • Crossing fingers then that the source disk is one sector smaller. However, if that's not the case, then how can I work around this? Is it a big issue if dd fails to copy the last sector? The drive is anyways damaged, with various bad sectors, so I don't expect that this will be the only missing bit.
    – landroni
    Jan 30, 2014 at 20:59

For ddrescue you can use a 250Gb drive, or make a file on a partition of that size if you have bigger drive handy. No need to do a rescue from disc to disc, you can always mount the disc image later on via the loop interface.

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