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Spotting a Dead Hard Drive

If a hard drive is not accessible by software such as the system BIOS, Windows' Disk Management, or other disk utilities it can be considered as truly dead and in need of physical data recovery. A dead drive will often display other symptoms, such as not spinning, clicking, or making other unusual noises.

A drive with these problems may have a damaged electronic board, read heads, motor, or damage to the magnetic media. A Data recovery company equipped with clean room facilities can usually repair the drive by replacing the damaged components, imaging the drive, and if required performing a logical file reconstruction.

The cost for this kind of data recovery can be hundreds, even thousands of Dollars, and is not guaranteed to be successful.

Physical Data Recovery Problems

The chances of successful data recovery depend on the extent of the damage. Data recovery from a platter that has been heated up to Curie temperature (770 degrees Celsius for iron) is not even theoretically possible as this temperature completely demagnetizes the platters.

Modern hard drives are surprisingly sturdy, often capable of handling shocks up to 300G, but a hard enough impact can still unbalanced the platters making data recovery very difficult. Such a shock will cause the platters to vibrate while spinning, and if the vertical component of the vibration is greater than the height at which read head flies the result is a permanent head crash, further damaging the surface and making it impossible to read the magnetic information. If there is any horizontal vibration the read head will be unable track properly.

Physical Data Recovery in Extreme Cases

Fortunately there is technology capable of overcoming all these problems. This is Magnetic Force Microscope (MFM) photography, the only route to data recovery that does not require the platters to spin. Instead MFM scans the entire surface of the platter moving from region to region, with each region yielding a picture. This pains taking process takes several months, and when it is finished these pictures have to be stitched together.

Consider that a 20GB hard drive consists of 160, 000, 000, 000 bits. Including overheads that could rise to around 300, 000, 000, 000 bits, with each individual bit represented by a magnetic flux change. Since each MFM picture displaying this flux change uses around 100 bytes, the result is 40 Terabytes of data to be analyzed. Data recovery by this means can cost 100, 000s of Dollars, but it can recover data where no other method can.

Drive Types Issues in Data Recovery

The type of drive also affects the chances of successful data Recovery, as most professional data recovery companies can only work on certain drives. After assembly a modern hard drive is conditioned to work perfectly with the read heads, platters etc. that are actually used. This means that it is not always possible to use parts from another drive, even if the replacement parts have same component number.

Andrew Whitehead is a contributor at Free-backup.info -- the home of the popular Amazon S3 based online backup service -- Back2zip. This article available at http://free-backup.info/physical-data-recovery.html