Written by Sümeyye Sever

In your computer system, you need to have some kind of persistent storage, such as a hard disk drive or a solid state device in order to retain data once your computer is shut down and powered off. Remember, the CPU's cache and the system memory or RAM is going to lose the data they contain whenever you power them down or shut down your computer because they're both considered to be volatile storage mechanisms, but non-volatile or persistent storage like hard disk drives and solid state devices, on the other hand, are going to be able to retain the data even if the system is shut down or powered off.

Hard Disk Drive (HDD)

• Hard disk drives are a form of mass storage device and a mass storage device is simply any kind of non-volatile storage device that can hold data when the system is powered down at a large scale. (GB, TB)
• HDD is a device that’s going to be storing data on a metal or glass platter that’s coated with a magnetic substance. This magnetic substance can then be charged with different electrical currents to be able to create data on those devices by storing ones and zeros on that magnetic substance.
• This is done on the platter and the platters are going to be accessed using a read write head that is actually moved by what is known as an actuator mechanism. We’re going to have to spin this platter around to be able to move actuator and read write head to the right location to read the data or write the data to the platter. This is what we refer to as seeking or retrieving the data.
• The faster you can sipin the hard disk, the faster you’re actually able to access the data that’s being stored on it. So when you’re trying to buy a hard disk drive you need to consider its speed as measured in RPMs or revolutions per minute because the higher speed is going to give you better drive performance. When you look at the hard disk drive you’re going to see generally four basic types of speeds that are out there. 5400 RPMs, 7200 RPMs, 10000 RPMs, 15000 RPMs.
• Now when you’re looking at a hard disk drive, another area you need to consider is its buffer size. Now the buffer size is an internal buffer or cache on that hard disk drive that allows the drive to cache a lof of the data to increase its overall performance as it’s seeking and reading new data.
• When it comes to installing your hard disk drive, you’re going to have to connect it to the motherboard using a cable, and the type of cable you’re going to use is going to depend on the form factor as well as the hard drive that you selected. In most modern systems you’re going to be using a SATA cable to connect your hard disk drive to your motherboard.

Solid State Drive (SDD)

• Uses flash memory technology to implement mass storage
• Because of this lack of mechanical components SSDs are much faster and more durable than a traditional hard drive.
• When it comes to SSDs, there are three main form factors you're going to come across.
  • 2.5 inch
    • Used when replacing an HDD inside a laptop or a small desktop
  • 1.8 inch
    • Used inside of small laptops
    • Been replaced by the M2 form factor
  • M2
    • It looks like a memory chip, small, sleek, and light
• When it comes to connecting your SSD, there are multiple different ways you can do this depending on which SSD you're using. Older SSDs rely on SATA connectors (7+15 pin SATA) Used in both 2.5 and 1.8 inch SSDs.
• Now, as an alternative to this, there was something developed called mSATA. mSATA is of smaller form factor that allows an SSD to be packaged as an adapter card that can be plugged into a combined data and power port on your motherboard.
• Now these SATA connectors can become a bottleneck for you though because SSDs are really fast and they can operate faster than SATA speeds. Because of this manufacturer created something known as NVMe.
• NVMe (Non-Volatile Memory Express) is a communication protocol used with M2 form factor to plug directly into the motherboard.
• In addition to SATA, mSATA, and NVMe, there's another one called PCIe, which stands for PCI Express or Peripheral Component Interconnect Express. Use PCIe slots on the motherboard. Those slots are faster than SATA but slower than NVMe. And so most SSDs these days are going to be installed as an M2 form factor using an NVMe connection to the motherboard.
• When it comes to SSDs, you’re going to get great performance but limited storage cabability based on the same price tag as a traditional hard drive. For this reason a lot of people will use a mixture of two devices, both in SSD to host their main OS and applications which require higher speeds, and then a lager mechanical hard drive to be able to store all of your large data files because it is a lot cheaper to do that on a traditional hard drive.