In some cases, you can recover data that you’ve accidentally deleted or overwritten on a Mac hard drive, and it’s often something you can do with special utility software. If you hard disk has encountered physical problems, you may need a specialist.
How Mac Files Are Stored
- Your Mac “writes” files to its hard disk as a series of ones and zeros, filling in available space on the drive. It then creates pointers to those files in a database called the directory. When you go to retrieve a particular file (by opening it in the Finder or an application) the directory is consulted and the data is read from the drive.
How Mac Files Are Deleted
- When Mac files are deleted (moved to the Trash and the Trash is emptied), those ones and zeroes aren’t actually “erased” or removed from the hard disk. Instead, the pointer in the disk directory is removed, which tells the Mac OS that it’s now OK to overwrite those “deleted” when new files are saved.
When Mac Files Are Overwritten
- If you’ve overwritten an existing file (by saving a different file with the same name), that can be more problematic–the Mac OS is allowed to immediately overwrite a file if it has the same file name. However, there are cases where files are not lost–particularly if you overwrite entire folders or you overwrite a large file with a smaller file.
Avoid Further Drive Activity
- If you find you’ve deleted a file you want to recover, stop writing data to that hard disk as quickly as possible. Generally, that means shutting down the Mac and not using it if the data was lost on your Mac’s main hard drive.
Recover Lost Files
- To recover files that have been deleted (or, if you’re lucky, overwritten) you will need a third-party application such as File Salvage, Data Rescue or Tech Tool Pro. Start up your Mac using the utility’s CD or DVD, then run a file scans on the drive to see if the utility can locate any deleted file data.
Recover From Hard Disk Failure
- If your Mac has encountered disk directory corruption, running a rebuilding utility such as Tech Tool Pro or DiskWarrior may allow you to rebuild the directory and recover the drive. In the worst case, the drive may be physically damaged, necessitating service by a specialist in file recovery such as DriveSavers.
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