Hard drive failures can occur at any time. We tell our clients that all hard drives that you own will fail one time or another.As long as you have at least one copy of the data contained on the hard drive you working, you should be fine. If the hard drive on which you are working by holes, you can always restore the backup onto another hard drive.
When a hard drive fails, stop immediately. From this point, assess the cost of your data. If you cannot replace the data or the data is more than the minimum cost of data recovery, send it to us immediately.
The more that you attempt your own type of data recovery, the more you will damage your drive. If the data is vital it is best to leave it up to us to try and recover it. We may have techniques that take 12 hours that may recover data that would take you weeks and weeks to recover even a small amount of data.Those weeks that you take trying to recover from a damage drive will more than likely damage the drive further.
If you have bad sectors on your hard drive, the read write heads will be repeatedly going over that area. This can cause the heads to scratch more and more information off every rotation. Eventually this was either scrape off so much information that data recovery is impossible, or that the drive has to be opened and the heads replaced.