Hard Disk: An Introduction
Hard Disks are used to store information. All information on computers are stored in files. Hard disks store the majority of information on today's modern computer. Hard disk drives (HDDs) can be critically damaged by static electricity, shock, and other factors, often resulting in failure or the loss of valuable data. In many cases it may become necessary to recover information from your hard drive. Such retrieval is quite possible.
Hard Disk Failure
*Physical Failures
Physical failure occurs from sudden switch off, power failure, sliding them off desks and cheap components. As for data loss, data is only magnetic impulses on the surface of a hard disk. And ridiculously small bits of magnetism at that! When the magnetic impulse fades, or changes position, trouble starts.
Drive Alignment Drift is another cause of problems. Mechanical devices are subject to wear and tear, heat and cold, loosening tolerances etc.
The small changes in the read/write heads wouldn't matter usually, as data still gets written in the same place as it will be read later. However, there is some data that hardly ever gets re-written, and that is the Sector ID Headers.
*Logical Failures
Master Boot Record Failure
Technically, when the Master Boot Record is working correctly, the master boot code scans the partition table for the active partition, finds the starting sector, loads a copy of the boot sector from the active partition into memory and then transfers control to the executable code in the boot sector. If the master boot code cannot complete these functions, the system displays a message similar to the MBR error.
*Boot Sector Failure
The boot sector is a region of a hard disk, floppy disk, and other similar data storage device. It is loaded to memory and executed as a part of the bootstrap sequence. The boot sector contains a small computer program that is loaded on the operating system into memory and transfers the control.
Most boot sector failure occurs by the defection of boot sector virus. Boot sector viruses are usually spread by infected floppy disks. In the past, these were usually bootable disks, but this is no longer the case. A floppy disk does not need to be bootable to transmit a boot virus. Any disk can cause infection if it is in the drive when the computer boots up or shuts down.
*Accidentally Deleted Data
Some time some how you may delete a file thinking we don?t need it any more, but in a week or or two you may realize that it is a needed one. It happens to the best of us, but fortunately there are ways to get these lost files back.
When it comes to data on your computer, it is almost impossible to accidentally remove it beyond recoverability. Even if you are intentionally trying to completely wipe a file from your hard drive it is exceedingly difficult.
*Cross Linked Files
A file system error that corrupts the contents of an existing file by writing data from another file into the same cluster. Running Scandisk or a similar program cleans up the problem, but one of the files is no longer usable.
*Bad Sectors
It is a portion of the Hard disk that cannot be used any more. If a part of the disk get bad sector which contains data then those data is to be recovered before use. When you format a disk, the OS will mark all the unusable sector as bad sector, however, this does not affect the overall performance of the disk as the damaged space is considered unusable.
Hard Disk Data Recovery
*Replace the (Circuit Board) PCB
Upon a Hard Drive circuit board failure, it is possible to get back the data by carefully replacing the PCB of the hard drive.
*Replace the Firmware
Hard disk firmware is the information that is used by the computer that allows it to correctly interact with the hard disk. It may be replaced or updated by the matching firmware.
*Replace the Head Stack
There are common situation that may be due to head failures. There is a small chip located in the head stack that is called PREAMPLIFIER. Working with preamplifiers always includes some difficulties, because, practically, they can not withstand static discharges. If re-soldering is needed, one should follow a number of rules to protect a preamplifier from static damage caused by careless finger touching. Although this task is very risky and it should be done in a high secured lab specially created for this task.
*Move the disk to another Drive
In some cases complete functionality of the Hard drive may be disabled while only the internal disk plate is without any damages or errors. In those situations, it is possible to move the disk to another drive.
*Spin-Stand Testers
Hard drive manufactures and their head media; preamplifier and read channel suppliers do have very accurate, very expensive "magic machines" called Spin-Stands. These are used for testing and experimenting with heads and disks. They are used mostly by researcher and development departments.
*Magnetic Force Microscopes (MFM)
Magnetic force microscopy is a powerful tool for high-resolution magnetic imaging of most data storage media. As the density of magnetic media is higher, the bit becomes smaller than the wavelength of light, so optical techniques can not resolve it. General MFM is capable of imaging the magnetic domain of several tens of nanometers. Also, MFM is almost simultaneous with measuring the surface characteristics of topography and roughness of the same area with sub-angstrom vertical resolution.
Recovery Softwares
*SpinRite 6.0
SpinRite is a stand-alone DOS program designed to refurbish hard drives, floppy disks and recover data from marginally or completely unreadable hard drives and floppy disks and from partitions and folders which have become unreadable.
*Ontrack data recovery software
Ontrack Data Recovery offers the industry's highest quality and cost-effective do-it-yourself data recovery software solutions for almost any data loss situation covering servers, desktops or laptops for all media, operating systems and file types. Ontrack's EasyRecoveryTM family of products is unmatched in its ability to recover/repair from all causes of lost data.
*Recover My Files
Recover My Files data recovery software will easily recover deleted files emptied from the Windows Recycle Bin, or lost due to the format or corruption of a hard drive, virus or Trojan infection, and unexpected system shutdown or software failure.
Data Recovery Over Hard Disk Failure
by: Muneer Mohammad
