Why Hard Drives Fail

Steve Smith takes you on a guide tour of a hard drive, and explains why it may fail, and how it may fail in the near future.

Should you change your hard drives more often and make backups?

Episode # 3-19 available on : Youtube Blip.tv Vimeo 
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Released: February 3, 2013

Hard drives, spin, crash, and die. Its a fact of life, but instead of explaining why a hard drive can fail, I'm going to show you the inside of a hard drive, the platters, the readers, the reader arms, the printed circuit boards, and show you why everything can break anytime you need everything.

First, this is the only time I will be explaining this, don't open hard drives you have any attachment to, once this is done, any dust that falls on the surface can render the data unreadable by the reader heads.

Opening a drive is fairly hard to do, and newer ones use special screws that can keep most people out, mainly because you may lack the correct screw drivers to open them up. Hard drive companies, also, hide screws under stickers to make sure you didn't screw them up yourself.

Newer hard drives use unique PCBs, or printed circuit boards, that have a unique id for the series of platters of disks inside your hard drive. This makes it impossible to simply swipe your burnt PCB from a bad drive with another since it would not be able to identify which platter is actually which. Even if you could actually figure out which is which, there is not necessarily a viable way of telling the chips this, since I presume they must be read only after they have been completed.

The PCB is responsible for several tasks, but the two most important tasks are turning the primary servo to make the disk platters spin, and controlling the many control arms supporting the reader heads. The reader heads move as one, so all the heads must wait after the others before collecting the data required, instead of allowing independent movement. If the reader heads moved independently, this would speed up a little the drive, however, it would make the drive harder to make, and more likely to fail.

Hard drive platters are double sided, meaning they store data on both sides, meaning there is twice as many reader heads, as there are disk platters.

The primary disk platter servo can bring a hard drive up to speed at 7200RPM in most traditional hard drives, less for some 2.5 inch models like for laptops which normally spin at 5400RPM, and the fastest consumer drives spin from 9600 to 10000 RPM.

The PCB has several other features like SMART, which stands for Self-Monitoring, Analysis and Reporting Technology. SMART was created to allow computers to detect if hard drives are in working order, or failing. SMART is only effective under load, and can only diagnose data it is currently scanning for, and nothing else.

The PCB is, also, responsible for error correction. Data is stored as magnetic information on the hard drive, but many environmental factors can distort or destroy the data on the disk. Static electricity, magnetic interference, solar radiation, gravitational forces, such as being dropped or tumbled, can render portions of the hard drive unreadable. All hard drives, even new ones have to error correct. When the level of error correction exceeds a set limit, SMART notifies us that the drive is failing, however, like I said before, SMART, and therefore all other technologies can only be useful under load to provide us with accurate information.

Hard drives prone to most of these issues are normally in laptops, but any hard drive can, and will, fail. The reason why laptops have more issues are because of heat and gravitational forces. We tend to bounce around our laptops, and these machines are barely cool enough to run. Hard drives are, also, not rated for continued and permanent use. In fact, very few computers, main boards, hard drives, etc... are rated for such continual use, and such use may void the warranty. Enterprise level hardware may be designed for such use when bought for those specific purposes.

For laptops, if you move yours around often, changing the HDD to a SSD may provide a better more long lasting solution for your laptop, and would allow for cooler and faster operation of your laptop. Remember to disable virtual memory, if you proceed with this method.

The issues I just named are typically related to the hard drive platters, there are, also, other forms of hard drive failure, or hard failures that can occur. These include the possibility that the PCB fails, or any of the two, or both of the servos that control the platter spin, or reader heads fail. Failure of any of these three components is equal to, or worst than any wear down to the hard drive platters, and can render the hard drive dead without warning. A number known and unknown factors can be attributed to the death of these pieces, and prevention methods cannot completely eliminate the risks. Gravitational force damage, electrical issues due to power from the utilities, power supply, etc... can cause damage to the hard drive components, so fixing or preventing any issues is hard but not impossible. Using an UPS, and/or higher quality power supply may provided some protection from electrical issues.

Little known fact, the reader heads, don't actually touch the hard drive platter, they merely float above it, and read the magnetic signal from the air between the disk and the reader head.

Next week, I talk again about RAM, but this time, I explain why Windows refuses to run when it detects bad ram, and how the blue screen of death is related to this eventuality.

Remember to like this episode if you were interested in today's topic, share if you think someone else could benefit from the topic, and subscribe if you want to learn more. For the show notes of this episode and others, for more information on other ways to subscribe to our show, to subscribe to our weekly newsletter, and how to participate by submitting your questions, comments, suggestions, and stories, head over to TQAWeekly.com.

Host : Steve Smith | Music : Jonny Lee Hart | Editor : Steve Smith | Producer : Zed Axis Productions

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Posted by ask
February 3, 2013

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