Re: [sleuthkit-users] You opinion needed on clicking harddisk (withvideo)

[Svein Y. W. <sv...@wi...>]

 
> I have this portable harddisk which has "died".
> No important data is on it.  So experimenting with the disk for
> educational purposes is no problem.
> I have opened the disk to check what the clicking noise exactly was.
> I have made a short video of this:
> 
> http://www.youtube.com/watch?v=yFz8K-eODUA

Unfortunately I was not able to open your video, but in general: 

"Clicking sounds" is a very common failure mode for hard drives. The
explanation goes back to the way hard drives are made. 

The r/w head is mounted on the end of an arm above the platters. The arm is
fixed to an actuator. The actuator moves the arm, thereby moving the r/w
head from one track to another. The positioning of the arm is determined by
using a feedback of the signal read from the disk: In order to accurately
position the head above a data track, the signal stored on the track is
amplified and fed back into the actuator to move the head into a position
where it is at the centre of the track. Due to the very small size of the
tracks, this system works much better than any mechanical or pre-programmed
positioning of the tracks.

Now, consider what happens if one of the heads stops working: there will no
longer be a signal to amplify, and it will no longer be possible for the
actuator to position the read/write head above a track. In this situation,
the arm with the r/w head will search for tracks in vain and will inevitably
crash with the centre-spindle, causing the click sound. In most cases, the
disk controller will try again a number of times before it gives up, causing
a number of repeated click sounds.

R/w-heads are very sensitive electromechanical devices, so although there
could also be other explanations, the most likely reason for this failure
mode is one or more defective r/w heads. Defects in r/w heads may be caused
by electric shock (even small static voltages may cause damage), crash
(often due to movement while the unit was operational), heat or perhaps
other reasons.


Regards,

Svein Willassen
Researcher, Department of Telematics
Norwegian University of Science and Technology