A computer has two types of memory. There’s primary memory and secondary memory. Now primary memory is temporary, which is RAM. But secondary memory is permanent, and this deals with storage drives. Now every computer needs a place to store its data. Whether that data is photos, documents, video, and audio files, or an operating system, a computer needs a place to store this data internally on a storage drive. And these drives also need to be non-volatile, which means that they will retain the data even if the power is turned off. And there are different types of internal storage drives that a computer uses. And these drives could be magnetic hard drives, solid-state drives, or hybrid drives. So let’s first talk about magnetic hard drives. Now magnetic hard drives have been around since the beginning of computers. They were introduced by IBM in 1956 and even though they’ve been around for a long time, they are still used today. The hard disk drive is a sealed case that contains magnetic disks and these disks are where the actual data is stored on. These disks rotate at high speeds and as they do, the actuator arm will either write data to the disks or read data from the disks, depending upon what the user wants to These magnetic disks can rotate at high speeds of either 5400, 7200, or 10,000 RPM. The typical the hard drive that’s used today in desktop computers operates at the 7200 RPM range. A cheaper desktop hard drive operates at 5400 RPM, which is also the speed of a typical laptop hard Higher-end hard drives would operate at10,000 RPM.
However, these higher-end hard drives are not commonly used anymore because of the advanced speeds of solid-state drives, which we’ll talk about next. Hard drives today use the serial ATA interface. Now, this is a newer standard that is faster than the outdated parallel ATA interface. So instead of data traveling in a parallel path, the data travels in a serial path, which means that the data travels one bit at a time. SATA drives have transfer speeds averaging 6 gigabits per second, which is considerably faster than the old parallel ATA. And hard drives also come in two physical sizes. They come in 3.5 or 2.5 inches. 3.5-inch drives are what desktop computers and servers will use and 2.5-inch drives are what laptops will use. Another type of storage device is called an SSD or solid-state drive.
Now, these drives have no moving parts. So instead of using magnetic disks, these drives use flash memory chips to store data. So the data transfer is very fast. And in addition, since they have no moving parts, they are also very quiet and more energy efficient. SSDs also come in different form factors. They would come in a standard 2.5-inch rectangular form factor or they would come in the newer M.2 form factor. Now both of these drives store data on flash memory but they connect to the motherboard using different interfaces.
SSDs are also more resistant to physical shock compared to hard drives, whereas if you were to physically shock a hard drive, such as dropping it or jolting your computer, it could crash the drive and your data would be lost. SSDs are also more expensive than hard drives, but you do get what you pay for them because they are considerably faster and you’ll see a big difference in the performance of your computer. And they can also be used on both desktop and laptop computers. Now because of the price difference between SSDs and hard drives, a lot of times if you were to buy a new computer, the computer may come with both an SSD drive and a hard drive. The faster SSD would be a smaller capacity drive that would contain any data that would benefit from the speed and that you would access frequently, such as the operating system, programs, and documents. And the slower hard drive would be a larger capacity drive that would be used for secondary storage. For example, to store data that you would access less frequently or the drive would be used to store large files such as videos. Now you could buy or build a computer with one large SSD for all of your storage,
but that would significantly increase the price of the computer and it’s almost pointless to have files that you infrequently access on an SSD. So this is why, to save money, computers will use both an SSD and a hard drive. Now there is also a solution where you can have an SSD and a hard drive as one physical drive instead of two separate drives. And these are called SSHD or solid-state hybrid drives.
Now, these drives combine the use of magnetic disks and flash memory. Hybrid drives take advantage of the large capacity and the low cost of magnetic disks, with the speed of an SSD. In a hybrid drive, the magnetic disks would be used to store data, while the flash memory would be used for the caching of the data. And these drives are pretty much automatic. The firmware in the drive will learn and decide by itself as to where the data will be stored. The files that are accessed frequently, will be cached and stored on the flash memory, while the infrequently used data will be stored on the disks.