What are harddrives? And how does the type of harddrive affect the performance of your computer?

Harddrives are a type of storage hardware. In a vast majority of consumer desktops and laptops, harddrives are the primary storage medium. For further information about harddrives and other storage hardware, refer to the following article:

Harddrive store your computer’s operating system (Windows, Mac OSX, Linux, Ubuntu etc.) and allows your computer to function. Besides storing your operating system, your primary harddrive also stores any programs installed on your computer. Oftentimes people store their media and documents on their harddrive as well.

As a fuction of the fact that harddrives contain your operating system, the health of your harddrive is one major predictor of the speed of your computer. If your harddrive ceases to function properly your computer will not function at all; this is because your computer cannot run without a readable operating system.

The read and write speeds on your harddrive are determinants of how fast your computer starts up and how fast any program on that harddrive will load. The read and write speeds also determine how fast files or folders are moved from one place on the hardrive to another (through copy/paste for example) and how long it takes for programs to install on your computer.

What determines read and write speeds?

First of all there are two types of harddrives that are common it today’s laptops and desktops. One is the mechanical harddrive that utilizes a spinning disk and a read write header, the other is a solid-state drive (an SSD) which incorporates no moving parts, but simply uses a PCB. SSD’s have higher read/write speeds than even the best mechanical harddrives, but their speed comes at a premium price. SSD’s have a much higher cost to capacity ratio.

For a mechanical harddrive specifically the factors that determine read and write speeds are: (1) the size of the disk, (2) the rotational speed of the disk. Aside from these, the following factors affect the speed of both SSD’s and mechanical harddrives: (3) type of data connector, (4) overall physical health of the drive.

For a mechanical harddrive that uses a disk to store data, one would suspect that a bigger disk would lead to greater performance. This is because we are conditioned to believing that bigger is better. However, in this case, the logic of bigger = better does not apply. A larger disk actually leads to slower read write speeds because the read write head has to move a greater distance in order to read from and write to the disk. In terms of performance larger disks do not help at all. On the other hand, larger disks can more effectively store a greater capacity of data.

Higher rotational speed of a mechanical harddrive’s disk leads to greater read write speeds as the read/write head can move to the correct spot to create or retrieve data faster. Higher rotational speeds come with a risk however: with higher rotational speed the disk is more prone to damage and the harddrive is more prone to failure. Laptop harddrives tend to always have lower rotational speeds than desktop harddrives; this is because laptops are moved around a lot, increasing risk of harddrive failure, whereas desktop harddrives tend to be more firmly seated in the machine and desktops are seldom moved from place to place. The higher rotational speeds on desktop harddrives mean that desktops have superior performance to laptop harddrives.

Types of data connectors

There are three types of data connectors that are used in home PCs nowadays, they are: USB, SATA and PCI-E. Of the three PCI-E is the least prevalent and most niche, generally used by gamers and people who require a lot of performance from their computer.

SATA connector is by far the most prevalent type of data connector. If you have an internal harddrive in your laptop or desktop and you bought it sometime after 2000, it is highly likely that your harddrive uses a SATA connector. SATA connection is the second fastest kind of connection for home computers after the more niche PCI-E type connections.

A USB connection for harddrives are used primarily by external harddrives. Internal harddrives forgo the slower speeds of USB connection in order to take advantage of the faster transfer rate of SATA connection.

When you plug in an external harddrive or thumb drive into a USB slot, that usb connection has a dual purpose; The USB connection provides power the external drive, and it works as a data connector. The result of this is that occasionally external drives can be power starved. Internal harddrives on the other hand, use SATA connection exclusively for its data connection and it uses a separate power connector which often plugs directly to your computer’s power supply. Power is seldom an issue for internal harddrives.

USB connections have significantly lower transfer rates than SATA connection. It is due to this slower speed that USB storage devices are seldom ever used to store programs or to store bootable operating systems. If programs are stored on a USB storage device, those programs will load more sluggishly than if they were stored in an internal harddrive with SATA connection. If a primary operating system is stored in a USB storage device, the computer will start up much more slowly than if it were stored on a regular internal harddrive.

The disadvantage of slower speed of USB connection type is partially counteracted by the ease of use of USB connections. Several USB slots are almost always available on modern computers. Unlike SATA or PCI-E connection slots, USB slots are located directly on the external chassis on most desktops and laptops. This means that users do not have to open up the computer to access them. Home users without a lot of experience opening up computers can easily use these USB slots to connect their external storage device. This ease of use makes external storage devices ideal for storing backups of important files, or for storage of non-program documents.

Now, last but not least is the PCI-E connector. Out of all the connection types, PCI-E connectors have the largest connectors and they are the least available connector type. PCI-E connection ports sit directly on your computer’s motherboard. The number of PCI-E slots available on the motherboard is directly associated with how big your motherboard is. By extension, the size of your motherboard is also a good predictor of how big your overall system’s size is. Small computers with small motherboards can have as low as one PCI-E slot, while large home or server desktops can have motherboards that have upto 6 or 7 PCI-E slots. PCI-E slots on smaller computers and laptops can be in short supply as the PCI-E slots are capable of not only connecting special PCI-E harddrives, but can also be used to connect video cards, audio cards, RAID cards or a number of other niche hardware components.

Harddrives that connect to the computer via. PCI-E connection have considerably higher read and write speeds than regular SATA connected harddrives. Harddrives that utilize PCI-E tend to be nearly identical in design to SSD’s; only difference being they are slightly bigger and have the PCI-E connector instead of SATA connector. PCI-E harddrives are also the most expensive out of all harddrive types for home computers.


Harddrives come in a variety of types and have different speeds and performance thresholds. It is upto you, the user, to decide what type of harddrive best suits your needs. Harddrives are the components that have the most significant impact on a computer’s performance, especially for low end users who use mostly word Processing software and browsers. For high end users, the computer’s performance is a combination of CPU power, video processing power as well as harddrive read write speeds. It is important for users to become educated about computer components so they can make purchasing decisions that have the biggest impact on their computer’s performance.

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