Storage Devices – CompTIA A+ 220-1101 – 3.3

There are many ways to store and access files on our computing devices. In this video, you’ll learn about hard drives, solid state drives, flash memory, and optical drives.

One way to store a lot of information on our computing devices is through the use of a hard drive. A hard drive consists of spinning magnetic platters. And even when your system is powered off, it still retains the data that you’ve stored on that hard drive.

Because of that, you often hear hard drives referred to as “non-volatile” because the information continues to be on that drive even when there’s no power to the system. That means that we could power on our system and access any bit of data that may be on this hard drive. We don’t have to forward or rewind information like you might with a tape drive. And that’s why we refer to access on a hard drive as “random access.”

Inside the drive itself are a lot of moving parts. You’ve got platters that are constantly spinning. You’ve got actuator arms that are moving back and forth to find the data that’s on this drive. And all of these mechanical components create limitations on how quickly we can retrieve and store data on this storage device.

Another concern is that any time there’s moving parts, these moving parts will eventually break. And so we know that a hard drive will eventually fail. The question is exactly when that failure might occur.

Here’s the view inside of a hard drive. All of the data is stored on these platters that are spinning at very high rates of speed. That platter is rotating around a spindle that’s in the middle of the platters. And an actuator on the hard drive controls an arm that moves back and forth over these platters to be able to store or retrieve data.

There’s a small head at the end of the arm that is used to very precisely locate, retrieve, and write data to the spinning platters. These platters can spin at different speeds. And the faster they spin, the faster you’ll be able to retrieve the data.

For example, a common rotational speed for a low-end hard drive is 5,400 rotations per minute. And that gives you a rotational latency of about 5 and 1/2 milliseconds. This means as the platter is spinning around, we have to wait for the data to eventually make its way back to the head so that you can either read or write that data.

If the drive is spinning faster, for example, at 15,000 rotations per minute, then the rotational latency lowers to about 2 milliseconds. So the faster you spin this drive, the faster you’ll be able to read or write the data that’s on that drive.

Here’s a better view from the side. You can see there’s not just a single platter, there are multiple platters. And indeed, there are multiple heads connected to both the top and the bottom of every platter. This allows you to read and write data from every single available spot on these spinning platters.

You may find different sizes for storage devices on your systems. It’s very common on larger desktop computers to find 3-and-1/2 inch drives, like the hard drive that we see here. You might also find 2-and-1/2 inch drives on that same desktop platform and very commonly in laptop platforms. And on newer systems, whether they’re desktop or laptop systems, you may find an M.2 drive, which is much smaller than the 3-and-1/2 or 2-and-1/2 inch drives.

The evolution of storage has begun moving us away from the spinning mechanical hard drives into a system that has no moving parts at all. This is referring, of course, to a solid-state drive, or SSD. Again, we have non-volatile memory that’s inside of this, so we can power off our system and our data remains on these SSDs. And there’s no moving parts inside of these SSDs, so we don’t have to worry about a mechanical failure causing problems being able to read and write from the storage device.

One significant and very obvious advantage to an SSD is that the performance is so much faster than a traditional hard drive. We don’t have to worry about the revolutions per minute or the amount of data that we can transfer as these platters are spinning around. Instead with an SSD, we can access data directly and retrieve it at extremely high rates of speed.

As SSDs have improved over time, one of the things we found is that the interface we use to access the SSD is an important part of the overall performance. One common type of interface that we use on our hard drives is a SATA interface, so it makes sense that we might have a SATA interface also available for an SSD. This means that we could remove a SATA drive from a desktop or a laptop and simply replace it with an SSD that has the same type of SATA interface.

One of the advantages of having a laptop or mobile device is that they’re very portable. And if you can make the components inside of that device smaller, then you can decrease the overall size of that device. With SATA, we were originally limited by the size of a spinning drive. And the 3-and-1/2 or 2-and-1/2 inch SATA drives took up quite a bit of room inside of our mobile devices.

So we created a new interface for SATA called mSATA. This stands for mini-SATA. Instead of having a spinning drive inside of a case, we can take that SSD memory and put it on a much smaller component.

It’s not unusual to find mSATA drives inside of mobile devices or even some desktop systems. But when we introduce the M.2 interface, we decided that that would be a much more reasonable and much smaller type of component. And you’ll find that mSATA interfaces are not very common on new devices today.

Here’s a view of an mSATA drive installed inside of a laptop. And you can see that it doesn’t take up much space. It’s certainly much smaller than installing a full-sized 2-and-1/2 inch drive inside of this chassis. This provided a great way to shrink down the overall size of these devices, and certainly contributed to the ability to have much more mobile devices containing much larger amounts of storage space.

But one of the challenges with SATA is that it was originally designed to transfer data from hard drives. SATA uses a protocol known as AHCI. This stands for the Advanced Host Controller Interface that moves data from the storage drive into the memory of your system. This SATA revision 3, for example, can have throughputs up to 600 megabytes per second. But our SSDs can exceed these values, which means connecting to a SATA interface may be limiting your throughput to an SSD.

For that reason, we created a new way to communicate to our SSD called NVMe. This is Non-volatile Memory Express. And it’s designed to match the throughputs that you would need for technologies such as an SSD.

This means we’ll have lower latency and much higher throughput when communicating to these high-speed SSDs, which also means that we can really take advantage of the full capabilities of that technology. Since this is not a SATA connection, then we’re not connecting our SSD to a SATA interface. Instead, we’re using a type of interface called an M.2 interface.

There are a number of advantages with using M.2 instead of using a traditional SATA connection. One of the first advantages is that this is a much smaller form factor than SATA. This has a single connection to the motherboard. And you can see there’s no external power that’s required. It simply pulls the power from the motherboard itself.

This M.2 interface can also directly connect to the PCI Express bus that is in your computer, providing much higher throughput than you would get through something like a SATA interface. It’s very common to see 4 gigabytes per second throughput when you’re using an NVMe with your SSD through a by 4 PCIe interface.

If you’re planning to use this type of drive on your system, then you should also know that there’s more than one type of M.2 interface. We refer to these keys that are in the interface with different names. There’s a B key, the M key. And some M.2 interfaces will support the B and the M key.

So to get the best possible throughput for an M.2-based SSD, you want to be sure that your system can support NVMe. Your M.2 interface may only be using the traditional AHCI throughput that you might see with a SATA connection. So you’ll need to check the documentation for your motherboard to see exactly what’s supported.

Your motherboard might also only support one type of M.2 key. It may be an M key or a B key, so you need to make sure that you’re buying the right M.2-based SSD for your motherboard. Here’s a close-up of that SSD. And you can see that this SSD model supports a motherboard that can take an M key SSD or a B key SSD.

Installing an M.2 drive on your motherboard is relatively straightforward. You would first find the M.2 interface on the motherboard and slide the SSD into that slot. You then fasten the SSD to the drive using a screw that’s on the other end of the SSD.

Another type of storage that we use extensively on our laptops and desktop computers is flash memory. Technically, this is an EEPROM, which is an electrically erasable programmable read-only memory. This is also a non-volatile form of storage, so you can remove the flash drive from your system. There’s no power going to the flash drive, yet it’s able to retain all of the data we’ve stored in that flash memory.

One concern with flash memory is that it does have a limit to the number of times you can write information to that drive. Once you hit that threshold, you’re able to read the information that is on that flash drive, but you would not be able to rewrite or change any of that information in the future.

It’s also not recommended to use flash drives as archival storage. These are very small storage devices, and they can be easily lost or damaged. It’s always good to have a backup of all of your data, but especially data that you’re storing on a flash drive.

Here are some very common examples of flash memory. Your USB flash drive that you’re probably familiar with is up here in the upper left. And if you have a camera or some other mobile device, you may also be using an SD type of flash memory. If you have a mobile phone or a very small device, it might use a very small version of the SD called a microSD. And for older systems, you may find some legacy flash drives, such as the compact flash or the xD picture card.

Another type of storage that is becoming increasingly difficult to find on our systems is an optical drive. This is a storage type that uses a laser to either read small pits or different colors that are on this individual optical disk. This is a very common type of storage to use for archival media, especially if it’s a media type that you would not want to change once it’s been written.

There are many different formats of optical drives. But some of the most popular are CD-ROMs, DVD-ROMs, or Blu-ray. And you’ll find optical drives as an option available for internal laptop or desktop use. And there are also external drives that can connect via USB to those systems as well.