Data Recovery is the process of rescuing the data from the spoiled or inaccessible storage media when the media reaches a situation where it cannot be accessed in the normal manner. The data often can be rescued from the storage media formats such as Floppy Disks, Hard Disks, Tape Drives, CDs, DVDs and RAID Drives. The data is lost either due to the Physical damage to the storage disk or the logical damage to the file system in the disk that prevents it from being accessible by the operating system.

Physical Damage

Physical damage is the corruption of the physical parts of the storage media. There are a variety of possibilities like the improper working of a Hard disk due to the mechanical failures such as head crashes, failed motors or insufficient power supply. CD Rom drives can have their layers scratched off, the tape drives can simply break when kept inside a bag while traveling are a few to name and there can be many more reasons. Physical hard drive damage always leads to some kind of Logical damage as well as there are some clusters destroyed which are inaccessible. The logical damage must be recovered before any files are salvaged from the media.

The physical damages cannot be repaired by the user himself as it can cause further damage to the media and moreover the users generally are not trained to handle such extreme processes like opening a hard disk in a normal room can further damage the disk as it leads to dust settlement on the surface of the disk. To overcome these difficulties the Data Recovery Companies are consulted where clean room facilities at 100 percent are maintained to protect the media when the repairs are being carried out. This helps in rebuilding the logical damage before the data is being rescued. However the data recovery success rate is below 100 percent in case of a physical damage but most of the files are recovered. This kind of recovery can also be carried out for other media such as Tape drives, memory cards etc.

Logical Damage

The Logical damages occur more commonly when compared to that of the Physical damage. This is primarily caused due improper maintenance where the file system structures are prevented from being completely written to the storage medium. This results in the inconsistency in the state of file system and can cause variety of problems such as system crashes, operating system checking for the boot file for more than one time or there can also be an actual data loss. These inconsistencies up to a limited stage can be repaired and there are various programs that are accompanied with the operating software and can be used to overcome the problem. For instance there is chkdsk with Microsoft Windows and fsck with Linux and also some software available to overcome these errors when the operating system is unable to correct these errors.

While most of the logical damage can be recovered by the operating system or a good data recovery software. This usually happen when during a recovery process two files claims to share the same allocation unit and in such case, data loss for one of the files is essentially guaranteed. This can be lowered by use of journaling file systems, such as NTFS 5.0. These file systems can always be rolled back to a consistent state, which means the data that will be lost will be likely the one in the drives cache during the system failure. However, regular system maintenance should still be followed to avoid any kind of data loss. This not only protects from the data being lost but also from the file system being infected by the virus. However, one incompatibility still remains where the disk controller reports that the file system reports of structures being saved to the disk when it has not actually occurred. This can often happen during a power loss where the data is stored in cache. This problem can be solved by using a system that is equipped with a battery backup or an Uninterrupted Power Supply (UPS) so that the waiting data can be written when the power is restored or at least to give enough time to the system to shut down properly.

For more information on most typical data recovery cases and various data recovery software available click on the respective links.