Introduction to Data Recovery
The last twenty years has witnessed an incredible rise in the use of computers in the USA. Once solely the servant of the public and commercial sectors, computer technology has pervaded our society to the extent where it is thought that at least 85% of people in the USA use computers. Indeed, it seems difficult now to recall a time when people did not rely on computers and other technology to work, bank, shop and communicate with others. The development of computer technology has improved at a rate commensurate with our increased reliance on them. Over time computers have become smaller, faster and able to store greatly increased volumes of data on their hard drives. However, although hard drives are continuously being improved by manufacturers, they do remain vulnerable to failure and have a shelf life of around three years. A study conducted by McGladrey and Pullen purported that one of every five hundred data center’s will suffer severe data loss this year and, as a consequence, almost half of these will go out of business.
How do hard disks work?
A hard disk drive is a storage device that digitally encodes data using read-write heads onto disks called platters. The platters rotate at very high speeds as the heads code data to them or retrieve data from them. Thus the disks operate under high stress and the chances of failure increase the longer the disk is in operational use. As manufacturers continually seek to improve the responsiveness of computers the disks are placed under greater strain. Today’s hard disks rotate at 15,000 rpm , a speed that generates enormous centrifugal force and increases the potential for disk malfunction.
How do hard disks fail?
Hard disk failures fall into two basic categories: physical problems with the disk or corruption of the information stored on the disk. Within those categories there are several reasons disks may fail as outlined below:
1. Mechanical failure
2. Logical errors
3. Firmware corruption
4. Electronic failure and controller board malfunction
5. Human error
6. Problems in other parts of the computer
Among the most serious forms of hard disk failure, mechanical failures can range from motor problems to head crashes and often lead to data loss which in some cases can be severe or even complete. Head crashes are the most common form of mechanical failure and occur when, as the name suggests, the read-write heads collide with the hard disk platters often causing damage to both heads and platters. In normal operation the heads ride on an extremely thin layer of moving air above the magnetic surface of the platter. However, electrical surges, dust particles or sudden movements of the computer can cause the head to collide with the disk, damaging the magnetic covering of the disk and causing the data stored to become unreadable. Although head crashes are a serious form of hard disk failure, you can sometimes make a full recovery using cutting edge technologies.
Logical errors differ from mechanical failure in that there is nothing physically wrong with the disk. In these cases the problem lies with the information stored on the disk, for example there could be an invalid entry on the FAT (file allocation table). Logical errors tend to be not as serious in nature as mechanical faults and are addressed with the use of professional software tools. Some widely available software tools that purport to resolve these errors can often make the problem worse and render the data completely unrecoverable.
Firmware corruption does not cause any physical damage to the data stored on the drive, it merely prevents the computer from accessing the data. Firmware is software that is integrated into the hardware of the disk drive. It is responsible for controlling configuration, powering on and off and interaction between the component parts of the system. When the disk is powered on, the hard disk loads data from the firmware zone into RAM. If there is a problem during this process then the drive will not be able to access data from the hard drive.
Electronic Failure and Controller Board Malfunction
Electronic failure is similar to firmware corruption in that it creates accessibility problems rather than actually causing physical damage to the stored data. Hard drives have a circuit board known as the controller board which is responsible for providing the power to and controlling the mechanical unit. The controller board is made up of electronic circuits and chips that can develop internal fissures if exposed to temperatures that are too variable. These fissures can cause electronic failure rendering the controller board inoperable. Alternatively an electronic failure may be caused by the computer suffering a power surge from mains electricity. Electronic failures are characterized by the hard disk being undetectable to the BIOS and the data is usually fully recoverable as it is not corrupted.
While some users accidentally overwrite important data and need to investigate the possibilities of retrieving the original data, most human error is indirect in that they mistreat their computer hardware. As previously mentioned, hard disk failure can be caused by temperature variations, internal dust, power spikes and knocks and bumps. Users need to take care of the environment in which they use their machines to prevent these types of occurrences.
Problems in other parts of the computer
Computers are sophisticated machines that are made up of a variety of components. Problems in other areas of the computer can have an effect on the performance of the hard disk. Three common causes of problems are: inappropriate BIOS configuration, IDE cable malfunction and power connector problems. 1. Inappropriate BIOS configuration – If the BIOS is not configured properly it may seem that the disk is not working properly. By setting the hard disk type to AUTO in the BIOS set up utility this problem will be resolved.
IDE cable malfunction
IDE flat ribbon cables can be quite brittle and can become defective and this has a knock on effect on the hard disk performance. This cable should be checked if hard disk problems are experienced.
Power connector problems
A poor quality or malfunctioning power connector could mean that the hard disk is not being properly powered. Again if hard disk problems are experienced it is worth checking the power connector.
With all of these three problems there is no damage to the data stored on the disk so when they are resolved the data can be retrieved.