Data recovery is the process of restoring or retrieving data that has been lost, accidentally deleted or inaccessible for some reason. Data recovery can occur in 2 cases, one reason is due to physical damage of the secondary storage medium, and the other is due to logical damage I.e. corruption of the files in the medium. The most common situation is due to operating system failure or accidental damage. This can be done by using copying the data to a backup medium such as a live cd, etc.
The next situation is disk failure. In this case data cannot be read easily. So depending on the type of situation different techniques is used. In case of hardware based recovery, the disk has to be changed permanently, in case the hard disk recovery is needed, the data which can be read only can be salvaged. In case of software based recovery, the file system or hard disk has to be repaired and the technique will vary depending on the extent of damage.
And the third situation is where the files are deleted from the secondary storage medium. In this case the files which are deleted will not be permanently deleted in the disk but their reference in the directory will be deleted. The space allotted for these files will be available until they are over written, these files maybe recoverable.
Preventing data loss
The first step to prevent data loss is to have a backup of the data. Firewalls and virus protection software should be used. And software or hardware should not be upgraded without having a backup. Software’s like free data recovery and memory card recovery help you to recover lost files and data which were either destroyed or deleted accidentally.
Data recovery techniques
- use of software to recover data
Data recovery software scans sectors of hard drive and restructures the file system either in memory or another hard drive. The software can be used to copy the recoverable data to the destined location. By making the complete sector copy of the hard drive, most data recovery programs search for deleted files to undeleted files. If the files are corrupt or defective, this method will not work. Some data recovery programs will ignore this and search all of the unallocated clusters to try to find and recover files.
- use of machines to recover data
The user may send a failed hard disk to a private data recovery company that offers secure and confidential data recovery. The company will carefully perform part replacements of the heads, spindle motor and base casting, the electronic boards, etc. in a clean, dry environment.
Part replacement has been successful for data recovery about 40% – 60% of the time. When data is written to the medium, the head sets the polarity of most, but not all of the magnetic domains.
When a 1 is written to disk the media records a 1, and when a 0 is written the media records a 0. However the actual effectis closer to obtaining a 0.95 when a 0 is overwritten with a 1, and a 1.05 when a 1 is overwritten with a 1.
Normal disk circuitry is set up so that both these values are read as ones, but using specialized circuitry it is possible to work out what previous layers contained.
The recovery of at least one or two layers of overwritten data isn’t too hard to perform by reading the signal from the analog head electronics, and analyzing it in software to recover the previously recorded signal.