Computer Hard Drive Definition + SSD and SSHD

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This page is a computer hard drive definition and is dedicated for those that are unsure what a hard drive is and what to gain a basic understanding.

If you have read the page on the definition of Main Memory, you will know that that is volatile memory type. This means that when the computer loses power, all data stored in main memory will be lost. This, however, is not the case with hard drives. Data can be stored for long periods of time, with or without power.

Once referred to as a Winchester drive, a hard drive is a type of magnetic storage device that has the capability to hold large amounts of data. Inside the hard drive casing, there are plates or disks that spin whilst connected to a power source. The HDD speed is determined by the amount of revolutions per minute (RPM). A spindle is used to read a track, which is a line that data can be read from. Tracks are then separated into sectors. Think of it as an old record player. The player has a record disk and it works by the needle touching the record and outputting the recorded track. And not to forget, the read/write head. This has to placed quickly on the selected track.record player - computer hard drive definition

A standard desktop size HDD is 3.5-inches in diameter with 2.5-inches being the preferred size in laptops. In terms of data size, the most common sizes you find in laptops and desktops are between 500GB and 2Tb, but they can be higher or lower.

Typically, though, hard drives are not the fastest component inside your PC. Much of your PC boot time will depend on your hard Drive speed because it has to fetch and load the operating system as well as all your files and directories. In terms of computing, the faster the component, the smaller the amount of memory and the higher the price will be.

Fortunately, there have been some improvements in technology over the past few years with the introduction of faster hard drives such as hybrid drives and SSDs (Solid State Drives). SSDs are designed differently to normal hard drives. They have less moving mechanical parts and they also have their own processor chip; making processing data a lot faster. Because of the way an SSD is built it is more reliable, energy efficient and also quieter. But, the main drawback is that they are more expensive, gigabyte for gigabyte. At this moment in time (2017), a 4 GB SSD will set you back 2 Grand. The diameter size of an SSD is 2.5-inches and requires a bracket case in order to be correctly fitted in a desktop PC. More modern cases have such mounts built-in.

A Hybrid drive, otherwise known as a Solid State Hard Drive (SSHD) are essentially the best of both hard drives and solid state drives. What that means is that an SSHD will be cheaper than an SSD gigabyte for gigabyte, but although it won’t be as quick as one, it will be much faster than a standard HDD. Typically, an SSHD will contain a large HDD, such as a 1 Tb as well as an SSD that will have a small amount of storage; usually 8 GB. That might not seem a lot, but the purpose of the hybrid drive is that it caches your most used data the SSD for much faster data reads. Another great thing about the hybrid drive is that it can potentially increase the lifespan of your drives by writing to the HDD when it needs to, instead of the SSD which does not like being constantly written to.


Hopefully, this computer hard drive definition made sense. If you have any queries, don’t fret to ask. I’ll usually respond to queries within 24 hours.