What Size External Hard Disk Drive Should You Buy?

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What Size External Hard Disk Drive Should You Buy?

Using an external hard disk drive is a great way to backup data and keep your files portable. Sizes and designs vary and have evolved a great deal over the last few decades. The first hard drive, designed by IBM in 1956 for the RAMAC 305 system, held 5 megabytes of data. The system was the same size as two big fridges. In 1980, the company introduced the first gigabyte hard drive. It was the size of a single fridge, weighed about 250 kilograms, and cost tens of thousands of dollars. By 2006, hard drives looked more like those we know today. Seagate's Barracuda 7200.10 was the largest on offer, with 750 gigabytes of storage space. Today, external hard drives are lightweight, compact, and sleek in design, with storage space of up to a few terabytes.

To find the right size of external hard disk drive for you, learn about the sizes available and how many files can be stored on each version. Take secondary features, such as power, connections, and design into account. External hard disk drives are available from a range of sources, including computer and electronics stores and online sites, such as eBay..

Understanding Gigabytes and Terabytes

Understanding how data sizes are expressed is important when choosing an external hard disk drive. A bit is the smallest unit of data that a computer uses. A byte is made up of 8 bits. For units larger than a byte, there are at least three accepted definitions for each term. When it comes to storage space, only two are pertinent. When describing disk storage capacity, a kilobyte (KB) is accepted to be 1,000 bytes. However, when describing process or virtual storage, a kilobyte is seen as approximately 1024 bytes. Hard drive manufacturers use the 1 kilobytes equals 1,000 bytes rule. However, Microsoft uses the other rule. This means that your hard drive's storage capacity is displayed on your computer as smaller than the manufacturer's specifications.

The table below provides a summary of common denotations and their equivalent sizes as applied to hard disk drive storage capacities.



1 bit

Smallest unit of data

1 byte

8 bits

1 kilobyte (KB)

1,000 bytes

1 megabyte (MB)

1,000 kilobytes

1 gigabyte (GB)

1,000 megabytes

1 terabyte (TB)

1,000 gigabytes

In the early days of computing, hard drives that could store several hundred megabytes of data were considered large. Today, it is more common to see hard drives with capacities measured in several hundred gigabytes or a few terabytes. A terabyte can hold about 3.6 million 300 kilobyte images or 300 hours of high quality video.

Storage Capacity for External Hard Disk Drives

External hard disk drives come in a variety of sizes, from 100GB to more than 8TB. The size of the hard drive chosen depends on what you need to store. A file's size can be influenced by a variety of factors, but it comes down to the amount of information stored in the file. The more information stored, the larger the file. Word processing documents tend to range from a few kilobytes to a few megabytes, depending on the length of the document and whether images are included. Photos typically fall between 2 to 5 MB, depending on the image quality. One song is, on average, approximately 5 MB. Movies can take up anywhere from 700 MB to several gigabytes, depending on whether the file is compressed.

Storage for Various Content

Taking these guideline file sizes into account, a user who needs an external hard disk drive to store only word processing documents or spreadsheets could buy a 300 GB hard drive and never fill it. However, someone who wants to back up movies may not be able to fit his or her whole collection on the drive. According to hard drive manufacturer Western Digital, a 500 GB hard drive can store about 100,000 digital photos taken with a 6-megapixel camera, or 125,000 MP3 tracks encoded as 128 kilobytes per second files.

Value for Money

Another aspect to take into account when deciding on the size of your external hard disk drive is value for money. The per byte storage bought becomes cheaper as the size of the hard drive increases. You are guaranteed to pay less per byte when buying a 1 TB hard disk drive than you are when buying a 300GB drive. If you have any doubts, it is better to buy a drive that is slightly bigger than required as additional storage space is never a bad thing. Should your storage needs change over time, your hard drive then has adequate storage space for additional files.

Factors to Consider When Buying an External Hard Disk Drive

While storage capacity is one of the most important factors to consider when buying an external hard disk drive, there are a few other factors. These affect portability, ease of use, and durability.

Form Factor of an External Hard Disk Drive

An external hard disk drive's form factor is determined by the type of hard drive used. Common form factors include 3.5,, 2.5,, 1.8,, and 1-inch drives. The smaller the form factor, the more portable and compact the device. Desktop drives are designed to be used in a stationary setting and tend to feature 3.5-inch drives. The higher the form factor, the higher the storage capacity.

Spindle Speed of an External Hard Disk Drive

Spindle speed, or revolutions per minute (rpm), indicates how many times the drive rotates in a minute and is an important performance indicator. Speeds for external hard disk drives vary from 3,600 to 10,000 rpm. Higher speeds usually mean better performance.

Drive Cache of an External Hard Disk Drive

Cache refers to the high-speed random access memory (RAM) built into the drive. This is used as a buffer between the computer system and the hard drive. More is better as this usually means better performance.

Interface of an External Hard Disk Drive

The interface featured determines how the drive is connected to the computer. Universal system bus (USB)) and FireWire ports are the most common options. Choose the best data transfer performance offered and take note of bandwidths available. Smaller form factor drives tend to have only one type of port; make sure the port matches your computer.

Power Source for an External Hard Disk Drive

Some external hard disk drives draw power directly from the USB or FireWire port, while others require an external power source. If you would like a more mobile device, choose one that does not require an external source. Ensure that enough power points are available to use the device comfortably.

How to Buy an External Hard Disk Drive on eBay

Buying on eBay is easy. Type a key phrase, for example "&", into the search bar, which is located conveniently on every page, to see the items offered by eBay sellers. Narrow your search results by choosing the most appropriate category and item features. If you would like more control over your search, use the advanced search option.

Before You Buy on eBay

Before buying on eBay, learn about the item and the seller. Simply click on an individual listing to view the item listing page where you can find all the information you need to do this. This includes the full item description, buying choices, payment options, the terms of the seller's returns policy, postage and packaging costs, and the seller's feedback information. If you have any questions about a listing, click on the "Ask a question&" link to contact the seller.

eBay ' s seller feedback feature makes it easy to get to know the seller before you buy. On the item listing page, click on the number next to the seller's username to view his or her feedback details. This information lets you know what previous buyers thought of a specific seller's products and customer service.


An external hard disk drive is a great way to store and backup important files. The right size for you depends on your needs and the type of data you intend to store. If you want a drive only for storing Word or Excel documents a smaller drive is adequate. However, photos, music, and video storage generally require a higher capacity drive. Remember that hard drive manufacturers use a different measuring rule to software developers. The drive may appear smaller than the manufacturer specified once it has been plugged into the system. It is better to buy a drive that is too big rather than too small, so if in doubt choose the bigger drive. In addition, the cost per byte usually decreases as storage capacity increases.

While storage capacity is important, a number of other factors should be taken into account when buying an external hard disk drive. The form factor generally dictates the drive's maximum capacity and portability. The larger the form factor, the higher the storage capacity. The smaller the form factor, the more compact the design on offer. Some desktop drives require an additional power supply to work.

Most external hard disk drives come with USB ports, FireWire ports, or both. Smaller drives may feature only one of these. Always choose a port that is compatible with your computer. Performance is affected by the spindle speed, bandwidth, and data transfer rate. For higher performance, look for higher specifications. eBay sellers offer a wide variety of external hard disk drives.

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