An Overview of Storage Devices – CompTIA A+ 220-801: 1.5

| September 10, 2012


Your computer has many options for the storage and retrieval of your important files. In this video, you’ll learn about the most popular options for PC storage.

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Review Quiz: An Overview of Storage Devices

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A hard drive is one of the most common storage devices we’ll find in our computers, because they store such a large amount of data. There are a lot of different kinds of hard drive formats, you’ll find out here. The three examples here would be a SATA hard drive. Here is the interface on a PATA hard drive, and then here at the bottom is a SCSI hard drive.

Ultimately, they are storing and retrieving the same amount of information. We’re able to put it onto these spinning platters inside of these devices. The big differences between them, of course, is the interfaces that we use to access each one of these storage devices. You wouldn’t normally remove the cover of a hard drive because any type of dust is going to damage the drive itself.

For the purposes of illustration, let’s look at what’s on the inside of a hard disk drive. First you can see the platter, and usually there are multiple platters that are spinning. And they’re spinning around this spindle that’s in the middle, and they’re going at a very, very high rate of speed. You have this actuator on the hard drive that controls this arm, so that it can move back and forth.

Very much like a record that would have a needle on top of it. And then you have a head at the very end that is reading and writing information from these magnetic platters. The platters themselves are spinning very, very quickly on hard drives that we might have at home. They might be at 7200 RPM and slower.

For enterprise environments, it’s very common to see our drives that would run at 10,000, or even 15,000 rotations per minute. And as you can see by these latency numbers, the faster the spin, the faster you can get the data. As the drive goes a little bit slower to 7,200 and down to 4,800, you can see that your latency gets slower and slower.

And that’s why in your enterprise environment, where time is very sensitive, you might want to buy the additional high speed drives because the latency numbers are so small when retrieving that information. If we look at it from the side, you can really see the platters. Now, there are four platters on this particular model with the arm that’s on top of it, and the head that’s at the very end.

And those are spinning around very, very, very quickly. The head is really floating on a cushion of air that is right on top of that. So it’s not really touching that platter that’s right there. It’s really just above it at a very, very small microscopic level, even. We want to be sure that we’re not actually touching or damaging that particular platter with the head of the actuator.

If we were to look at the data and how it was stored on these hard drives, you would find a series of rings on each platter, and those are called tracks. Our head would move back and forth to the correct track to be able to read or write information. If we were to look directly through the drive, through all of the platters that are there, we would call that a cylinder.

And so all of the heads that are on each layer of this particular hard drive would be able to access that information on a particular track and a particular cylinder of the hard drive. Within each track, we separate each one of those tracks into clusters. Those clusters store a certain amount of information on each one of those.

So now we have both the cylinder that we’re going to on a particular track, and reading a particular cluster from that track. So we can keep a big index of where everything is located on that drive, and have our hard drive simply move the arm to the appropriate area to be able to read and write that information. One of the newest technologies is one called SSD. That stands for solid state drives.

We don’t have a spinning platter like we see in this picture here. Instead, there’s no platter at all. It is completely solid state. There’s no moving parts whatsoever. It’s all memory inside of this device. That means that we don’t have to worry about hard drives crashing. We don’t have to worry about motors not working any longer. We don’t have to worry about any parts inside of that device wearing over time.

We simply will read and write memory. And it’s very, very fast in how it works. One of the challenges with this is that currently this is an emerging technology, and if we were to calculate on a per gigabyte basis, the cost associated with this, we would find that this SS is still quite a bit higher than using the traditional hard drives.

That’s why we’ll still see a large number of moving hard drives out in the industry, but you can find in certain situations, especially for portable devices or for people that need very, very fast storage, the SSD may be financially feasible. When you start up your computer, the system has to know how to start up the operating system that’s on that hard drive.

So there’s a very small area at the very beginning of the hard drive. On the first sector, it’s very small. Only about 512 bytes in size. This is called the Master Boot Record, or the MBR. This Master Boot Record has a table of the partitions that are on the hard drive. It has a signature of the disk, so you can find that particular disk in compare it to others that are in the system.

And it has on there directions for starting the primary operating system on that particular drive. Another common type of storage media on our devices are optical formats. We have everything from CD ROMs to DVD ROMs, to Blu-ray discs that we use these days, but they all tend to work exactly the same way.

Within these disks, if we were able to get down at a very, very tiny level, we would see a series of bumps on this disk, and we use a laser beam to be able to read those bumps and know what type of data is encoded on that particular system. For CD ROMs, the type of encoding and the capacity we have would give us about 700 megabytes of storage on a single CD-ROM.

On DVD, which stands for Digital Versatile Disk, we can fit 4.7 gigabytes on a single layer. But you can also have multiple layers on this same optical disk, and a dual layer would give us 8.5 gigabytes of storage. If we were to look at Blu-ray, Blu-ray gives us a total of 25 gigabytes for a single layer, and in the cases where you would have a dual layer Blu-ray disc, we can fit 50 gigabytes of storage.

You can see as we have gotten more advanced storage mechanisms, we’ve seen the size and the capacities of these optical devices grow exponentially. Of course on our computers these days, we can burn our own optical media. We don’t have little bumps on the optical media that we are using.

Instead, we’re simply darkening a photo sensitive dye that is on the media itself, and we’re looking at the lighter or the darker areas to be able to read that with our optical readers. We would find this in something called a compact disc rewritable.

You’ll see that abbreviated as CD-RW, if you wanted to create a CD format. For DVD formats, we have DVD-R/RW, and there’s a dual layer, which is a DVD-R/DL. Blu-ray is also recordable as well. There’s a Blu-ray disc recordable, BD-R, and also, a Blu-ray disc recordable erasable, where you can not only write, but you can erase and then right something else onto that disk as well.

If you’ve worked with mobile devices, then you’ve probably worked with one of these flash memory formats. Flash memory has the nice characteristic of being able to store information on it, and then be able to remove it from a device and not require power to maintain the data that’s on that flash memory.

We almost are always accustomed to seeing these USB flash memory storage devices, and on older components, you’ll also find compact flash formats. You can see that’s a relatively large format when compared to some of these others. That’s in a 16 gigabyte. And of course, there are larger sizes of that as well. You also have this micro SD format. There’s an SD format.

There is a micro SD and a mini SD format that you might run into. Sometimes you can take those formats and plug them into even a USB reader to be able to see those. And here’s another nonstandard type of format. You don’t see this on many devices, which is an XD format. Very common to see that on portable cameras. It’s a very proprietary format, but one that you will run into every now and again.

Your hard drives, of course, don’t have to stay inside of your computer case. You can always plug them into an external hard drive adapter, where you simply slide the hard drive right into the device. Or sometimes the hard drives will be mounted inside of a carrying case, and it has its own external power, external connectors on the back of it.

And that way, you’re able to plug it into one system, and then physically move it to another computer to be able to read and write information. We don’t see floppy drives very much any longer, but back in the day, we had large, 8 inch floppy disks, 5 and 1/4 inch, and the ones that we’re most accustomed to seeing these days are the 3 and 1/2 inch floppy drives.

Floppy drives themselves are very difficult to even find on newer computers. You can very often purchase a USB connected floppy drive if you still need some way to read information off of this media, because the disks themselves, even though they’re very small, 3 and 1/2 inches, they’ll store 1.44 megabytes of information.

So if you have some of this older media are around, you can still read it with either a built in floppy disk drive, or something you might plug into a USB connection. Tape drives have been a very cost effective solution for backing up large systems, especially if you have a large amount of data stored in your environment. You’re able to use relatively inexpensive tapes and be able to use multiple versions of those.

You’re able to take those tapes, then, and move them off site. You’re able to rotate through different tapes so that you always have a secondary backup of your data. On your personal computer at home, and certainly on the computers at work, you’re probably using one or more different kinds of these storage devices.

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Category: CompTIA A+ 220-801

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