Apple Tips
Data Recovery
But it's not cheap, and there are no guarantees.
Data Recovery apps mentioned here most often are:
Some of these have a free "trial mode," that will tell you if there's anything to be recovered, and perhaps recover a single file. For more, you have to pay the $$.
You'll probably need another drive to receive anything it can recover. Of course, if the drive failed, you need a new one anyway.
Look for other apps or services under Data Recovery via Google or MacUpdate.com.
If a disk fails, or the file system on it is corrupted and can’t be repaired by Disk Utility (in your Applications/Utilities folder) or a heavy-duty 3rd-party disk repair app such as Disk Warrior, you may be able to recover some data with a specialized data recovery app, or an outside service.
These apps may also be used to recover files that have been deleted (and the trash emptied, unless it was done with a secure empty).
If the drive in question is running, Stop using the drive immediately to prevent further loss due to files being overwritten. The longer you use it, the more files will be overwritten and lost forever.
If the disk in question is in a Time Capsule, there’s a major complication: these apps, and most outside services, only work on drives you can connect directly to your Mac (via USB or FireWire). You can remove the drive from the Time Capsule (voiding the warranty) and place it in a disk enclosure such as the ones you can get from OWC or other such places. That makes it an ordinary external HD that you can connect to your Mac, so those apps can access it.
But don't expect to get a complete list of folders and files. You may get some of that, and/or a random list of files. You may get the original file names, and/or some assigned names (if the actual name couldn't be determined). Then you'll have to figure out what each one is, where it goes, and move it manually.
If you can, concentrate on the home folders inside the Users folder. That’s where your data resides. You won’t be able to use anything recovered from any system folders, or Applications, anyway.
Recovering Time Machine Backups, however, is not recommended unless you've also irretrievably lost the originals. Some of these apps do not appear to work on Time Machine backups, so try to check with the maker first.
Because of their complex structure (see How Time Machine Works its Magic for details), even if one of these apps can deal with the backups, you'll have the following additional problems:
•The recovered files will not be in Time Machine backup format, meaning you won't be able to continue backing-up to them, or to restore from them, or use them with Setup Assistant or Migration Assistant (but you should be able to copy individual items from them).
•You may get several copies of the same file, or several different versions of the same file, with no easy way to tell which is which.
•The recovered data may be many times the size of the backups, so may not fit on even the largest external disk.