Physical failures to HDDs

Monday, 17 October 2016 by Jennifer Duits

Over the many years I’ve been working in a clean room, I’ve grown quite familiar with hard drives and the many pros and cons they can present. Generally speaking, hard drives can be a pretty resistant medium when used correctly and a technology I confidently use for storing my personal files. However, I know bad things can happen to good data as I have witnessed countless damages and failures to these devices that can cause data loss.

In this post I will focus on physical issues in hard drives (HDDs) as the problems faced by this technology are completely different from those experienced by other alternatives available in the market, such as solid state drives (SSD).

Let’s get physical, physical

One of the most common physical data losses occurs at head assembly level, where the read and write mechanism is located. This is the most important section of the drive because it’s not only the fastest moving, but also the most delicate section.

Fortunately, one of the parts we don’t have to worry much about nowadays is the spindle. From what I see come through our clean room, I would suggest that manufacturers have continuously improved this section so that the failure count for this specific part of the drive has dropped consistently over the last few years.

Unfortunately, it’s the delicate heads that remain at risk. The head’s slider hovers over the platter at a minimal distance (less than a hair width above) where it continually records the new data being created. Any time the drive is hit, dropped, shaken, etc., it can cause damage to the platter and therefore to the data. If this happens, what follows is commonly known as a crash (a physical scratch in the platter which affects the access to the data).

It’s electrifying

Drives can also suffer from electronic failures. Spikes in the mains voltage can be transferred to the magnetic media on the platters through the HDD’s printed circuit board (PCB) and subsequently to the heads, causing magnetic damage (also known as media corruption).

Going for a dip?

Another common type of damage is due to water. HDDs have a breathing hole with a filter which is required to equalise pressure inside and outside of the drive. This means that if a drive is dipped in water for a few seconds, there normally isn’t a major problem. However if the drive is submerged for a longer period the water can filter through into the HDD because it is not fully sealed by design.

It’s a disk-o inferno

Another physical failure we often see is due to fire. While a short exposure to temperatures of 100° may not cause any major damage, a longer exposure at 200° will most likely create some corruption to the data. Exposure at 300° or higher can actually de-solder the electronic connections, and since HDDs and platters are made of aluminium, they can warp.

A further issue with fire damage that is often overlooked is that firefighters will use cold water to put the fire out, which not only causes water damage to the drive but also the extreme temperature change can cause further warping of the drive, extending the damage.

Is it game over?

So is data actually recoverable from any of these types of damage? Fortunately yes, though you’ll need the help of an expert who knows how to get the data back instead of risking further (and perhaps irreparable) damage.

There are many factors that can influence whether a recovery is possible or not. For example, a recovery will depend on how big or bad the crash is. Sometimes the electronics themselves might be damaged, but once the electronics are fixed, the drive itself may still be in a good enough condition to allow a recovery. The duration of the exposure (to fire or water) can also be a critical factor. In the cases of fire damage I’ve worked on in the clean room, I’d say about 80% of the cases are recoverable, showing only smoke damage which, with the right tools, I am able to overcome to extract the data.

Something to bear in mind is that laptops and desktops tend to be more protected from external damage as the casing means it will take longer for external agents to actually reach the drive, giving data a better chance for survival.

So what is normal?

All running drives should be fairly silent. Any unusual noises including clicking, hissing and scratching are a sure sign that the drive is damaged. You should stop using it immediately to prevent any further data loss.

The silver lining

All is not doom and gloom in hard drive land. From the regular influx of drives I see in the clean room, my personal view is that the HDDs are getting better and better in terms of manufacturing as we are seeing fewer crashes from these devices.

Though it is inevitable that a failure may occur, I believe HDDs are currently as reliable as any other media in the market and still a good option for storage requirements. Do you agree? No? Leave me a comment below as I’d love to hear your thoughts on this.

Author: Michal Cieslik