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We’re going to take a jaunt entirely out of sequence here, moving from circuits and silicon into larger scale components. Today we’re talking about hard disk drives. Why? Because it’s a fun and interesting technology, because I know a thing or two about it from first-hand experience, but mostly because I’ve got a book to return. And so we’ll take a quick dive into the world of hard disk drives to see what, as the bear over the mountain intended, we can see.
Note the term; usually, we refer to these things as ‘hard drives’ and don’t bother to distinguish what kind it is. In the olden days, you had a hard drive and you had a floppy drive. A hard disk drive (hereafter HDD) contains a spinning platter that has the information magnetically encoded on it. A floppy drive also had a spinning platter with information on it, but that spinning part was bendable. For all you youngsters out there your “Save” icon is supposed to look like a floppy disk. It dates back to the times when people actually saved files for storage on one of ’em. The structure of the disks was rigid, you didn’t see the floppy part until you took the thing apart.
These days we say Hard Disk Drive to differentiate it from a Solid State Drive (SSD). An SSD is composed of silicon like all the other circuits we’ve been talking about. HDDs are going out of style and they’re being supplanted by SSDs. Why? Because SSDs are faster and less liable to break. Your HDD is one of the few things in your computer that has actual moving parts.
The computer does most things in the silicon. The processor, the RAM, the video card, that stuff. The benefit of silicon logic is that you can keep shrinking the circuits, cramming more and more information into less space with less electricity required to run it. The problem with moving components is that eventually things like friction take their toll and they, well, they don’t move anymore. Let me tell you a story.
I work in an HDD component factory. One night, maybe six months after I started as a support tech, I went out to buy an external hard drive. Being a patriotic company man I picked up the Western Digital My Passport™ one terabyte external drive. I knew we made components for that one. (A quick side note about economics; it took me about a night’s work to pay for the drive. I couldn’t have done even our part of making the components that go into it for that price. The Division of Labor is real.) Excited as I was by a new toy I carried the thing around with me in my pocket.
The thing about my pocket is that it moves around a lot. It’s just not a good place to keep delicate electronics, even something like an external hard drive which is built to be moved around. Eventually, the thing just stopped working. I bought another one, two terabytes this time. I was more careful with it but the same thing eventually happened. I don’t blame Western Digital for that, I blame my rough handling. Even so, when I bought a third external drive, I bought an SSD.
While I’m at it, SSDs are also superior in terms of the time it takes to retrieve data. In a hard disk drive, you’ve got to wait for the disk to rotate around to the spot that has the data encoded on it before you can read it. In an SSD all you’re waiting on is the electricity. SSDs are more expensive; a quick spot check on the market and it looks like you’ll pay twice as much for half the storage space. Still, the difference in speed is notable when you’re doing something as simple as booting up your computer.
That forces us to ask, therefore, “Why would anyone use an HDD?” Cheapness is a virtue. It’s what your father tried to teach you; what with his almost preternatural ability to tell when someone’s turned up the thermostat. Let’s say you’re a corporation that has a whole lot of information to store, hereafter referred to ‘stupid whack data.’ Where do you store your stupid whack data? Right, you stick it in the cloud.
What’s the cloud? It’s a buzzword to put in your powerpoints so that people will think you’re hip to the new technologies. But once we get past the marketing scams what is it? The cloud is someone else’s computer. Rather than maintain the server yourself you just pay someone to keep your data for you. It’s less stupid than it sounds. Okay, you offload your stupid whack data onto a cloud service. They, in turn, need some sort of hard drives to store it.
How do they store the data? If access time is critical they’ll fill their servers with SSDs. Web hosts will do it that way; the difference in page load time is noticeable. Otherwise, it’s just cheaper for them to use HDDs, and a lot of them. Sure, the occasional drive breaks (the XKCD guy once calculated that Google’s data centers have a catastrophic HDD failure every couple minutes.) but your data storage corporation will also be using things like RAIDs to make sure they won’t lose your stupid whack data.
Do you recall when the NSA and it’s metadata collection was newly in-the-news? There’s an NSA facility out in Utah that has enormous amounts of storage. The best guess is that it can handle between three and twelve exabytes of data. (‘Exa’ comes after ‘peta’ which comes after ‘tera’ which comes after ‘giga’. Ten exabytes means that pocket hard-drive I had times ten million, or roughly the difference between my bank account and Jeff Bezos’s.) We spent a slow night at work running the math on exactly how long the factory would be open building parts solely for the hard disk drives that’d go into that facility. The total was something like eight months.
I seem to have gotten this far without actually discussing how HDDs work, and how you could build one. Hope you found the discussion enlightening regardless. We’ll get to specifics of how the technology works next time. Join us fortnight next for “Spinning your Disks” or “Not that kind of RAID.”
This is part twenty two of my ongoing series on building a computer, the Christmas Miracle way. You may find previous parts under the tag How to Build a Computer. This week’s post has been brought to you by Ricochet’s own Group Writing! December’s theme is Veneration and there are plenty of spots waiting for you to fill one. Do your Group Writing today!