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Data Recovery Basics

Data Recovery Basics
All of us who have used computers at work or at home for any length of time have encountered the maddening experience of losing or accidentally deleting a file that we need. Incidentally, data recovery is a necessity of modern life.
Luckily, all modern operating systems have a built in automatic data recovery utility. But, what if the data itself has been corrupted or we lose a file in a complex system without an undelete option? Ill attempt to answer that very question as well as, 'What is data recovery?' 'Who does data recovery?' and 'How is data recovery accomplished?'

Data recovery is the process of restoring a file system. The file system and file structure are maintained by the operating system. The operating system maintains a record of every file stored on a disk as well as where that file is located in the disk memory space. You can think of the operating systems record of every file as a list of pointers to the space in memory where each file begins.

When a file is deleted, the operating system goes into its list of pointers and removes the pointer to that file. The file itself has not moved and it still inhabits the same place in memory completely unchanged. The only thing that has changed is that the operating system has removed the record of that file from the list of pointers and made that memory space available, or free if you will, to other files to be saved in the future.

So, when you hit the undelete button, what youre doing is telling the operating system to put the pointer to your lost file back into its record of pointers and back into your file structure. Unfortunately, if another file had been saved before you tried to undelete, it may have overwritten part of your lost file. This along with the complexities of some data and file systems as well as the value of the data itself may require the skills of a professional data recovery company.


Data recovery companies employ engineers with years of training and experience working with different file systems and hardware. The best data recovery companies use proprietary tools to restore the file structure on different file systems. If the data file itself has been corrupted, they use specialized software to repair the file depending on its type and amount of damage. They may each have their own tools for recovering lost data but they all follow the same basic steps.

The first step is to diagnose the problem. Was the data lost by accidental deletion, is the file system corrupted, or is there a problem with the disk or other hardware? If the problem is with the hardware, the disk may have to be taken into a clean room. The clean room is a room where the microscopic dirt and dust is kept down to a point where it cannot damage the microscopic electronics and components of computer hardware. A hardware engineer will work on the disk and get it operational without affecting whats actually stored on the disk.

Once the disk is operational, the data recovery engineers will make a copy of the entire disk. Then they can start restoring the file structure and make a list of all the directories and files on the disk. They will also test each file for damage and make repairs if possible. Finally, they can put the restored file system and repaired files on a new drive for the customer.

As you can see, the process of data recovery is a simple one, but the tools and skills required are beyond the scope of the average Joe. Professional data recovery companies have to keep up with constantly changing technology including hardware and software and the skills necessary to do so only belong to highly trained engineers. Therefore, when choosing a data recovery specialist, you want to look for a company with a proven track record of success with the hardware and software you have.

Luke Garfield Respected computer scientist and author.

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