A disk (memory card, hard disk drive, USB stick) is considered damaged when some of its files are no longer available or in good state.
One should distinguish between:
- Unplayable files that are the results of a recording failure, just need to be repaired: Use Treasured
- Missing or bad files after a storage failure, will need to be recovered by reading the disk, then repaired.
What does "read the disk" mean?
To recover files or whole disks, you need to read the disk at low-level.
Computer operating systems offer a graphical representation of the files: the Finder or the Desktop.
You can also browse the file system through the command line with Terminal or MS-DOS command interpreter cmd.
But in case of a damaged disk, those two levels are "contaminated". We need to dig deeper and read directly the raw data written on the physical devices, by-passing the operating system.
At this low level, the information is no longer organized in folder and files, but in fixed-length blocks or sectors, a bit like a huge mosaic made of identical tiles.
The data of a file is contained by one or several tiles, sometimes millions of them. In the best case, tiles corresponding to a file are contiguous. But in a fragmented disk, a file can be scattered in many disjointed tiles, making it very difficult to recompose it.
Is the disk even readable?
A memory card or HDD is considered unreadable if, despite being connected to the computer, the disk icon doesn't show up in the Finder (or if it is not detected by Windows)
To maximize the chances of reading the card, try in a variety of conditions:a memory card can be unreadable on your Mac with an external card reader, but can work on a Windows PC. Or it can work with a card reader but not with another. Or it can fail then work when you insert it a few times.
Unreadable disks cannot be examined for conventional tools. You will have to use a data recovery service, either software or hardware, to bring your disk back to "readable" state. In the worst cases, it is not possible.
How to read a damaged disk?
Treasured is by far the preferred tool.
Use the other methods as alternative, or if you like to put your hands in dirt, and have plenty of time to do so.
- Disk Utility (Mac)
- photoRec, a free, open source utility (Mac, Windows) and a photoRec tutorial
- dd (Mac) and dd for Windows
- Use a commercial Data Recovery solution.
Why can Treasured do better than dedicated recovery tools?
Unlike data recovery services and tools that try to recover files, Treasured tries to recover media instead:
Container data is what data recover tools use to detect and recovery files. But what matters is not the container, but the content: audio and video media. Treasured is first and foremost a media detector.