Our whole business revolves around recovering data, but there are some failures that are just not recoverable. It’s best to know when you’re chasing a lost cause, so I have compiled some info about impossible data recoveries.
If you are using a hard drive now and don’t already have a backup then stop reading and start backing up ASAP. Seriously. If you’re all backed up then read on for details about impossible recoveries.
Dropping a hard drive can cause major internal damage. Many new drives have some protection built-in to help them survive minor drops and falls, but you cannot rely on it. If you drop a drive then there is a high chance that the delicate heads have hit the discs and caused catastrophic damage. A loud scraping noise is a common giveaway. It’s important to keep the drive switched off if you want any chance of recovery. You could cause more damage by powering the drive on too many times. The only way to find the extent of the damage is to open the top cover of the drive. This MUST happen in a cleanroom environment. If the drop didn’t ruin your drive then tiny particles of dust will!
When we use the words media damage we mean scratched discs. Modern hard drives have at least one coated glass disc. The layers contain a magnetic material which reacts to the read/write heads. The heads should never touch the disc but instead float above on a cushion of air. If you shock the drive during use it could force the heads onto the surface of the disc where they will rip off some of the coating. There is a chance that with some careful work we could swap the heads and recover most of the data. If the drive is instead powered on, the broken heads could scrape more and more coating from the discs making recovery impossible. Nobody can recover data from dust. It may be possible to access file fragments from the undamaged discs, but most files span all disc surfaces. Hard drives don’t fill up one disc and then move on to another.
Firmware is the software that controls a hard drive. What was once some simple code to translate commands between the computer and the discs is now many megabytes in size. In fact, the firmware was originally small enough to fit on a tiny ROM chip, but is now stored on hidden sectors of the disk. Any problems within this area of the disk will mean the hard drive won’t know how to function. It could start clicking when it fails to read the correct information, or it could just shut itself down. Access to firmware is difficult as each manufacturer creates their own unique versions. Also the firmware contents are closely guarded secrets. The manufacturers don’t release any documentation about how to repair firmware so we have built our own database of knowledge over the years. Still, if the damage to the firmware is bad enough that we can’t fix it then the whole drive becomes useless.
The new bogeyman of data recovery. Encryption scrambles all the data on the disk and won’t unscramble it without the correct code or password. If you forget the code, the data is gone for good. If the software that accepts the code stops working then the data could also be lost. Current industry-standard algorithms are so-far unbroken. If the password is unknown then decrypting a bitlocker drive or PGP encrypted drive usually involves finding / guessing the password first.
Although deleted files are usually recoverable, that is only true until you overwrite them. If you keep using a computer after deleting files then they are likely to get overwritten. There are also specialist tools to delete and then overwrite files on purpose, which leave no chance of recovery. In fact most recent advice suggests a simple zero-erase is enough to destroy the data beyond recovery. Any information to the contrary is either old or wrong. If a disk sector was able to hold on to old data, the manufacturers would be using that space as extra storage capacity.
Despite all these unrecoverable problems, they are often mis-diagnosed. Even big companies can get it wrong, so you may want to seek a second opinion. We don’t charge any extra for giving a second opinion, so get in touch. Or read about this second opinion that worked out brilliantly for one lucky user.