RECOVERY results were more varied for the four abused 2.5 inch external hard drives.

Two disks were rolled over by a 1,700kg car and hammered; the other two were thrown and kicked down a stairway.

The different results could be because different brands of external disks were used in the experiment.

Adroit Data Recovery Centre supplied IBM drives, while Kroll Ontrack supplied drives made by Samsung. All four disks were wrapped in generic external casing.

At the Adroit labs, an incredible thing happened. Recovery for both hard drives was 100 per cent successful - and it was done in less than two hours.

The external drive that was rolled over by the Toyota Estima and then hammered sustained read-write damage. The actuator arm and the reading head was twisted and badly misaligned. The spindle motor was slightly squashed.

The first thing Adroit did was replace the servo assembly - comprising an actuator arm, reading head and spindle motor. Only then could it rescue data from the disk.

As for the other drive thrown and kicked down the stairs, injuries were more severe: There were minor scratches on the disk platter, where data resides.

This is surprising as you would think that more violence would be inflicted by the 1,700kg car and hammer.

The disk that received the stairway treatment had damages to the read-write head. A safety catch next to the head was also broken from the vibration and impact. Its servo assembly, too, was replaced.

Over at Kroll Ontrack, results weren't that bright.

Data in the drive that was thrown and kicked down the stairs was not recoverable at all.

Kroll said the damage was simply too great. The reading head was completely crushed, and powering up the damaged drive scratched the platters, causing permanent damage to the data stored.

It goes against logic but powering up is probably a risky thing to do to resuscitate failed hard disks.

The internal glass platters, where data resides, spin at 5,400 revolutions per minute.

Powering up a damaged drive will risk scratching the surface of the platters, resulting in permanent data loss.

The drive ran over by the car and hammered, on the other hand, had a better recovery.

Kroll's engineers were able to get back 66 out of 87 files.

This story was first published in The Straits Times Digital Life on 27 May 2008.