Hard Disk Drives 101

The instructable will teach you the ins and outs of hard drives, how they work, what they're made of, how to take care of them, and how to fix them when they go wrong.

A hard drive is where data in the computer is stored. Theres two kinds of hard drives, Hard Disk Drives, or HDDs, and Solid State Drives, or SSDs. This Instructable will be mostly focusing on HDDs. HDDs work by having a magnetic disc called the platter, which is divided up into thousands of “pizza slices” called sectors, and rings called tracks.

This creates millions of cells that can be individually magnetically charged, either positive or negative. The read/write head can read and write to these cells, which are interpreted by the computer as 1s and 0s in binary, which is how most computers remember things.

Solid state drives work by using flash memory, the same technology in flash drives. In fact, SSDs are basically really nice flash drives. Flash memory works by having two transistors separated by a thin oxide layer. They can kind of trap a positive charge between them, or not, which the computer can read as a 1 or 0. This is an improvement over HDDs since it has no moving parts, and is much faster since it’s all circuits. But SSDs are much more expensive than HDDs, and they deteriorate with lots of writing to the memory. So unless you’re building a top of the line gaming PC, you should probably use HDDs.

HDDs don’t require much physical maintenance, you should leave them be. The problem is when they’re moved or shaken, as the arm can bounce and scratch the disc. Try not to move them if you can, and if you have to, move them slowly.

HDDs do require software maintenance through, there’s a couple of programs you should run every couple months to make sure your hard drive is in working order. First is a disk check, which just makes sure everything's working on the disc. You can do this in Windows, just go to the drive and right click on it’s properties. From there you can go to tools and check the disc for errors.

Another useful software test is defragging the hard drive. After you use a drive for a long time files get left all over the place. Defragging the drive puts them back in place which causes faster loading times. Through don’t defrag SSDs, it’ll wear them out by rewriting everything. Windows does do it normally, but it’s good to check when it’s scheduled.

Finally you should run a surface test every once and awhile to make sure that all the cells on your platter are in good condition. They can get worn out overtime either by physical damage, magnetic desensitizing, or just wear and tear. Below I’ve got a video where I scan a hard drive with HDDScan to make sure it’s in good quality.

HDDs do fail, and the best way to prepare is to backup your data beforehand. But when you do have problems with your hard drive there’s a couple of things you can do to troubleshoot.

The most common error message related to hard drives is on bootup the computer will say no boot media detected. This means the computer can’t find the hard drive, which can be caused by all sorts of things, from total disc failure to it not being plugged in. I’d recommend to first open up the case and make sure everything’s plugged in properly. If you hear clicking noises coming from the hard drive on startup it’s a bad sign. That means that the disc is physically injured, and that as it runs it’s scratching itself. If you don’t have your data backed up then getting your data off it will be difficult, depending on the state of the drive.

Hard drives can’t really be repaired after they’re scratched, as opening them in the first place damages the discs, so in most cases ordering a new drive is the right course of action . But if you follow proper maintenance procedure they should last a long time, and when you see failure coming, you’ll be able to replace it ahead of time.

Here's a video where I show you how to use HDDScan to perform a surface scan and check the quality of your hard drive. It got broken into two parts because of some editing hiccups, so just watch them in order.