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How Is Data Stored in Computers?
Before we look at how data is recovered, we must have a good idea of how data is stored in computers. Of course, we all know that data is stored on hard disks, CD/DVD media, Flash disks and Magnetic Tapes. Let us now go into a little more detail on how exactly the data is stored.

There are two key elements involved in recording and accessing data. First is the data itself that is recorded on the disk surface and the second is “file system” that keeps track of which data is recorded where. It is the file system that enables us to retrieve the written data when needed.

For example, a disk surface might be divided up into “sectors” of 512 Bytes (characters) in length, with each sector having a unique ID. The file system would “allocate” sectors for each write operation. These allocated sectors would typically not be contiguous sectors. Instead, a file’s data could be scattered all over the surface of the disk. It is the file system that keeps track of on which particular sectors the data for each file is recorded.

If the file system gets damaged, the data on the disk become inaccessible. If you somehow manage to read the info on contiguous sectors in sequence, you would simply get jumbled garbage.

You need both the file system record as well as the relevant file data to read the data in a meaningful manner. That tells us of one way data could be “lost”.

It is the read/write heads above the fast rotating platters of the disk drive that records data magnetically on disk surfaces. There is a thin film of air between the head and platter surface, and in normal operation, the head does not touch the surface.
How Do Data Get Lost?
As we saw in the last section, if file system gets damaged, data could be effectively lost.

Data could also get lost in other ways. For example, the read/write head could come in contact with disk platters and this would cause damage to the magnetic media on the platter surface. Or the motor that rotates the platters, or some other mechanical component in the drive, could fail.

There is also the too common phenomenon of human errors on the part of operators and administrative staff that could result in data loss. Then there are virus and other malicious attacks, including deliberate sabotage that could destroy data on the computers.

If you stop working with the damaged drive, there would be greater chances of recovering the apparently lost data. On the other hand, continued operation of the drive, or a do-it-yourself attempt at recovering the data, could aggravate the damage making it difficult and more expensive, or even impossible, to recover the data.
How Is Lost Data Recovered?
As we saw earlier, apparently lost data is not permanently gone from the disk. A raw image would still be on the disk surface and data recovery specialists extract this image and try to reconstruct the data from it.

They repair any damage to the file system and try to make meaning out of the image so extracted. They might also replace the damaged read/write head with a matching, healthy one, or move the platter to a matching, healthy disk drive. Or replace the damaged PCB controlling the drive.

Data recovery specialists work in completely dust free environments, such as a Class 100 Clean Room, to avoid dust settling on the disk surfaces. Even microscopic particles of dust could damage the data that are densely packed on the disk.

In essence, the data recovery specialists try to preserve the image on the disk platters and use different techniques to reconstruct the data represented by the image.
Call a Data Recovery Specialist in Case of Data Loss
Data recovery is one task that you should not attempt to do yourself. You could not only aggravate the data damage but also void the manufacturer’s warranty on the drive (if you open the sealed drive). On the other hand, manufacturers authorize trained data recovery specialists to open the drives without voiding the warranty.

Reputed data recovery firms would be constantly keeping up to date with latest developments in drive technology and data storage. Because of their training and experience, these specialists would also be aware of the possible dangers involved and could take necessary precautions.

Above all, they have to facilities and specialized tools required for the task.