A brief Introduction of Data Recovery [MiniTool Wiki]
Data recovery is the process of recovering lost data from hard drives, U disk, digital memory cards and other storage devices.
The Principles of Data Storage and Recovery
In reality, most people think they cannot recover the deleted or formatted data. As a matter of fact, however, the deleted data are still stored in the hard disk. Users who have knowledge about data recovery know how to recover lost data. And, as long as we know the principle of data storage, we will know how to retrieve lost data.
Reasons for Data Loss
Sector is the basic unit for storing hard disk data, and sector can be considered as a page of a book. Before using the hard disk, users should partition the disk so as to perfectly manage it. No matter which partitioning tools users use, the amount of partitions, the size of each partition, the starting position and other information are stored in the first sector of the hard disk (it refers to the mbr sector where partition table is saved). If the partition table gets damaged or lost due to many reasons including hard disk damage, virus invasion and so on, some partitions will be lost. At this time, users can re-calculate the size and location of partition according to the data characteristics, and then put the information on the partition table. Thus, the lost partition is back.
File Allocation Table
After partitioning hard disk, users should format partition to store data. And the formatting partition program will help to divide the partition into directory file allocation area and data area according to the partition size. File Allocation Table helps to record the properties and size of each file, and the location in data area. And users can deal with files according to the file allocation table. If the file allocation table gets damage, the system will think the file has been lost since it cannot locate the file.
When users store files on hard disk, the system will record file name, file size and other information on the file allocation table. After that, it will help to write the real content of the file on the data area. Thus, the task of storing a file has been completed.
When users delete a file, the system just writes a deleted flag in front of the file entry in file allocation table to show that the space the file occupied has been released and other files can use it. Therefore, if users want to get back deleted file, they just need to remove the deletion flag. Of course, users should ensure that the deleted data have not been overwritten by new data. Otherwise, there is no way to retrieve them.
Like deletion, the formatting operation only operates the file allocation table. But, formatting will add the deleted flag on all files, or empty the file allocation table. Thus, the system will think the hard drive is empty. As a matter of fact, formatting doesn't damage the data area. Therefore, as long as users turn to a data recovery tool, they can recover lost data.
Data recovery engineers often say that as long as the lost files are not overwritten, they can recover them.
From the disk storage feature, we will know that when we delete files, the system just makes a deleted flag in front of the file entry in file allocation table. But, formatting and low-level formatting will write the number 0 on the original data. Thus, original files have been overwritten.
After deleting a file, users can store new information on the space occupied by the file. At this time, although the name of the file whose contents have been deleted is still here, the information on its data area has been overwritten. Meanwhile, the deleted file in the file allocation table may haven been overwritten by new data, and the original file name no longer exists.
If users write new data on a formatted partition and the new data just overwrite some original data, the remaining information which has not been overwritten is likely to be reorganized and recovered.
In the same way, after cloning partition/disk and restoring system, data recovery engineers may recover some lost data as long as the space occupied by new data is smaller than the original partition space.
Data Loss Prevention
1: Never store all data on the same drive
There is no doubt that most word processors will automatically store files on the “My Documents”. In fact, this is the last place for storing files. If the operating system gets damaged due to many reasons (like computer virus invasion and software failure), the only way to solve this problem is to reformat the hard drive or reinstall the operating system. But, this solution will destroy all data on this drive.
Another low-cost solution is to install two drives in computer. Thus, if the operating system is damaged, users can use the second hard rive. If users want to buy a new computer, they can install this drive into the new machine.
If users don't accept the method of installing the second hard disk, they can buy an external hard drive since it can be used on all computers at any time. If needed, users only need to plug it on a USB port or firewire port.
2: Back up files regularly
Saving all files on the hard drive is not enough. Users had better store different files into different partitions. Besides, they need back up files regularly. Here, the professional backup software – MiniTool ShadowMaker can help you to perform a backup on a regular basis. Thus, they can ensure the security of files.
If users want to access the file at any time, they can make a second backup. If the data are very important, users can store it on the fireproof layer.
3: Avoid mistaken operation
Many times, we have to admit that data are lost due to users' mistaken operation. In fact, users can use the safeguard measures provided by word processor (like track changes) to avoid some problems. The most common data loss case is that users delete some information by mistake when editing files. Thus, after saving this file, the deleted part has been lost.
As a matter of fact, users can copy the file before editing. It is indeed an effective solution for solving data loss problems.