Hard disk drive fault analysis

Data recovery from drives that have suffered a physical failure require a structured analysis regime. This involves visual inspection, electronics diagnosis, firmware analysis and testing of the read-write heads.

Diagnosis is absolutely the most important stage of the data recovery process because a mis-diagnosis can severely change the outcome of a recovery. Some data recovery companies use an ad-hoc method of trying this and trying that but we believe that is not the way to diagnose a potential problem with a hard disk and so have developed this methodology. This list is not exhaustive but describes the main diagnosis system.
  • Electronics test

    The electronics board is removed and standard components are tested and where necessary signals are traced through the various points on the board to make sure all is correct. When a fault is found, then the original board is never used for a recovery but it will very often contain unique information that must be extracted and transferred to a fully working PCB. This is either done using software and hardware specifically designed for this purpose or the physical ROM chip is removed and the contents read using a ROM programmer. The contents of the ROM is written to another known working PCB.

  • Internal visual analysis

    The drive is opened in one of our clean air cabinets and visible surfaces are closely examined under magnification for signs of damage. Drives that have been dropped often have heads that have been dislodged or have broken off or leave 'speckle' marks on the platters. All missing heads must be accounted for before the drive is spun up. Loose heads or debris inside a drive can cause irreparable damage, rendering a drive unrecoverable within a very short time if the drive is spun up whilst debris is loose in the drive.

    The inside of the drive cavity is checked for debris from the remains of a head crash and the internal filters are examined for contamination as that also indicates head failures on non-visible surfaces. Small dentistry mirrors are used to look in places that are not directly accessible, such as the spaces between platters.

  • Head Test

    As a compliment to the platter examination, vital information can be obtained by microscopic examination of the heads. Careful examination of each head can determine if there is platter damage on one of the surfaces that are not easily viewable without removal of the platters. If there is debris in one or more of the heads, this can indicate media damage for the affected surfaces.

  • Disk drive analyser

    Some hard disk faults need analysis using a Disk Drive Analyser (or DDA), the DDA is an advanced, expensive and very fast oscilloscope, with speeds in the GHz bands they are designed for specifically for use in hard disk drive development and trouble shooting, it is a must-have for any serious data recovery company. When used correctly a lot of information about the health and status of the drive can be gleaned from the traces including head faults, bad media and platter damage.

  • Bus analyser

    A bus analyser monitors the protocol of data transferred between the hard disk under test and the computer. The protocol includes the commands sent to the drive, the response codes received from the drive and data written to or read from the drive. We use this mainly for hard disks that show firmware problems so we can determine the exact location of the problem is and what type of error is generated. This lets us target the exact sectors within a specific module that are causing the problem giving much more control than using standard software solutions. The most important aspect of this stage is identifying the correct response from errors codes. Attempting to write a firmware module with certain errors can render a drive totally inoperable.

  • Commercial equipment

    Other important tools are commercially available for example, hard disk firmware analysis tools such as the PC3000 from ACE Laboratory, ACE have been providing us with data recovery firmware analysis technology since 2002 and their software is the flagship of firmware analysis and repair, they also provide the 'data-extractor' add on for the PC3000 which is advanced hard disk imaging software that enables the best possible recovery. Imaging by head on all makes of drives, selective data imaging for most operating systems and advanced control of bad media. Owning the equipment is a small part of the process, having an understanding of hard disk firmware is absolutely vital. We have received many drives where incorrect firmware 'fixes' have rendered a drive inoperable. Most of them we have been able to repair, but sadly, not all.