Hard Disk Controller

The controller board on a hard disk drive is a multifunctional component required to do a variety of tasks which must be performed with perfectly for the otherwise erratic behaviour could occur. The main function of the controller board is to act as the interface between the hard disk drive and the host adaptor of the computer it is attached to. It must also maintain the precise platter rotation speed, control the read/write heads and maintain the operational parameters, such as the defect lists.

Modern disk drives are manufactured with an integrated disk controller board, but this was not always the case, with separate add-on cards inserted into a peripheral slot. The add-in cards were paired with the hard disk drive, which could lead to problems if the wrong card was used. The controller card is extremely important for data recovery, as it must function correctly in order to recover the data correctly.

Controller Failures

The main causes of failure are due to overheating or a power surge, which can damage the components on the controller board. Sometimes this damage may not be sufficient to stop the drive from working, but its behaviour may become erratic which could potentially lead to further issues.

Damage to the firmware or maintenance area can cause the drive to go offline randomly and power down. Controller card failures of all kinds should be addressed by a professional data recovery company, as specialist equipment is required to rebuild the drive into the correct working condition.

Function of Defect List

Each hard disk drive when manufactured usually has a number of defects, the location of which must is identified during the low-level factory format process and stored in the primary defect list (P-List). During a hard disk drive’s operational lifetime it will develop additional defects, which when detected are mark in the grown defect list (G-List) and swapped to a spare sector.

These defect lists are extremely important as they ensure the correct sectors are access for each read or write operation. A failure of the defect list will result in a wrong sectors being returned, which leads to a failure of the file system, and causes complications in the data recovery process.

Data Recovery and Controller Boards

Information about swapping controller boards following the failure of a hard drive is readily available on the internet. The drive firmware revision of a replacement board must match that of the donor board. However, just replacing the controller board will not make the drive work correctly, as the chip containing all the drive specific information must also be transferred. It is this process which requires expertise and specialist equipment, which mean that a professional data recovery company, such as DiskEng, are best qualified to undertake this work.

Following the failure of a hard disk drive controller board, it is best practise to power the computer down and consult with a data recovery company. Repeated attempts to recover the data through powering it up could result in additional failures occurring.

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