Feb 01 2007
Data recovery
The process of data recovery involves salvaging data from storage media like hard disk drives, storage tapes, RAID, DVDs and CDs that have been damaged or have stopped working. This process may also be used for forensic purposes to recover data that has been deleted from storage media.
One of the prime reasons of data loss is physical damage. For instance, hard disks can suffer from mechanical failure, storage tapes can break and CDs can be scratched. Once this happens, the end user becomes helpless. He has neither the equipment nor the expertise to retrieve data.
He can, of course, use data recovery programs but for this he needs some level of computer proficiency. The other option is to go to data recovery companies that have Class 100 clean room facilities. But these are quite expensive.
Besides physical damage, data can also be lost on account of logical damage. This is more common and is mainly caused by power outages. These outages do not allow file system structures to be written to the storage media. System crashes and problems with hardware and drivers too can cause similar problems.
A part of the problem can be addressed by the basic repair tools that come with operating systems. For example, Microsoft Windows comes with chkdsk, Linux provides fsck and Mac OS X has Disk Utility. Besides this, you also have the option of using utilities provided by third party providers. But you must know how to use them.
These repair programs usually use two techniques. The first involves scanning the logical structure of the disk to see if it is consistent with the given specifications. This is the technique that is used by both fsck and chkdsk. The problem is that if the file system is severely damaged, the consistency check may not work.
Besides this, there is also the danger of losing important data files if the end user is not well versed in system restore operations. One way to avoid this is by partitioning the operating system from the data. This keeps the data safe, and protected.
The second technique uses clues from undamaged file system structures to rebuild the file system from scratch. This technique is slower than the first one, but it can be used to recover data where the logical structures have been destroyed. However, you need a much higher degree of expertise to do this.
