Such errors are corrected by the disk without bothering the user or the host computer, retrying the read operation multiple times if necessary. Each has Error Correction Code (ECC) bits appended, and using these the disk firmware can correct read errors up to a certain number of consecutive bits. The space on a hard disk is made up of sectors, each 512 bytes, or for large disks, 4096 bytes long. Most of the techniques and utilities described below can be used equally on SSDs, but before doing so you should understand their unique features and problems by reading Under the Bonnet in All about SSDs.īefore proceeding, it's important to understand how hard disks handle errors. This is shown dramatically in a which demonstrates that you can give a hard disk a hard time simply by shouting at it! The pressure to deliver ever greater storage capacities means that disk vendors (both hard disks and Solid State Disks or SSDs) push the storage density to such a level that they can only just read the data back. Some of these tools can be DANGEROUS and should only be used in a kill-or-cure situation or if you are certain that a full system backup is available and you are sure you know what you are doing. If you search online there is a small chance you will find a third party decryptor exploiting shoddy coding, but if the ransomware author did a good job then your data will be encrypted with military grade encryption and the purveyor of the ransomware will have the only key. Futhermore, people who pay the ransom frequently don't get all their data back. If you're tempted to pay the ransom, be aware that there is no guarantee it will be honoured, and your cash will likely be going to fund further criminal activity. Your best bet is recovery from backups (you did make them, didn't you?).

If your disk has been encrypted by ransomware then none of the tools described in this page are likely to help you.

There are other tools that can be used which may be much more informative. data returned by a hard disk can give a useful indication of the health of a disk but its interpretation is vendor-specific and not fully documented. Often, a hard drive will be showing warning signs before it dies, such as running very slowly or random crashes or failure to boot. However, there are a few things you can try yourself, but bear in mind that they could make it more difficult for a specialist firm if they don't succeed.

If your data is irreplaceable then for a few hundred pounds a specialist data recovery firm can usually recover it from a faulty hard drive.

Mac hard drive diagnostic tool