External Hard Disk Drive Buying Guide

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External Hard Disk Drive Buying Guide

When the internal memory of a PC becomes full, computer users have many choices for expanding the storage space without resorting to replacing the entire PC. Personal computers have a limited number of internal slots for extra memory, but attaching an external hard disk drive (HDD) can add storage capacity to a PC. External disk drives are not only useful for adding storage capacity. These devices are often used to back up computers. The external hard disk is a relatively small drive that can be stored in a safe or fireproof box for data protection. Moreover, many HDDs offer additional security features, such as data encryption.

Computer owners can use several HDDs. For example, one might dedicate one unit to only audiovisual media and another one to standard documents and files. When purchasing an external HDD, it is essential to understand how these disk drives differ from solid-state drives (SSDs). One should also decide between a portable or regular external version and consider other factors including the interface, form factor, and storage capacity. Buyers can find a variety of external hard disk drives at very competitive prices on eBay.

Solid-State Drives vs. Hard Disk Drives

Before purchasing an external HDD, buyers should understand the difference between a hard disk drive and a solid-state drive (SSD). Both items are considered peripheral computer equipment, but they differ distinctly in how they are constructed, how they operate, and how much they cost.

Solid-State Drives

Solid-state drives are a newer type of drive. They are quite fast but also quite costly. Their expense is due, in a large part, to the technology. An SSD is purely digital in that there are no moving parts that can break or otherwise become damaged. Because of their construction, SSDs are lightweight and more rugged than HDDs. However, under normal use and with proper care, an SSD is not usually required for regular desktop applications.

Hard Disk Drives

Hard disk technology has been in use for over 50 years. Even though SSDs dominate the market, the demand for HDDs is not going away anytime soon, as HDDs still presents some advantages over SSDs. Hard disk drives feature moving parts, namely a moving head that reads data from a spinning magnetic platter, or disc. This movement is what makes the HDD slower when compared to a SSD. The movement also creates some sound vibration, and a bit of heat, although these are negligible. There are normally several platters inside today's HDDs, which are designed to hold much larger quantities of data when compared to the past. The platters spin continuously when the PC is powered on, regardless of whether or not any data is being accessed. The head moves only when it is retrieving or writing data. Because the moving parts can easily be knocked out of line by rough handling, care must be taken not to drop or even bump external HDDs when they are connected to the PC. An HDD comes in two basic formats: portable and stationary.

Portable External Hard Disk Drives

Portable drives are much like thumb-sized flash drives in that they are intended to be taken from one machine to another for file transfer. Their generally larger size allows portable drives to hold more than most commonly available flash drives. A portable external HDD is smaller than a desktop drive and usually pulls enough power from the USB port.

Desktop External Hard Disk Drives

A desktop external HDD is larger and generally has more storage capacity than a portable drive. It requires more power and often must be plugged into an electrical socket, as well as attached to the computer via USB ports. This is why these types of drives are not considered portable. An AC power source may not always be available, which would render a standard external HDD useless in some situations. However, there is no other reason why a desktop HDD cannot be moved from one location to another.

External Hard Disk Drive Form Factors

The 'form factor' is a fancy way of referring to the diameter of the disk drive. The most common sizes for HDDs are 1.8 inches, 2.5 inches, 3.5 inches, and 5.25 inches. These sizes initially corresponded to the measurements of physical disks. The larger sizes correspond to the larger desktop drives, whereas the smaller ones are pocket-sized portable drives. In a sense, desktop drives are still somewhat portable. After all, they are considerably smaller than laptop PCs. However, as mentioned, this type of drive needs to be plugged into a wall socket for it to be used.

External Hard Disk Drive Storage Capacity

Storage sizes of external HDDs have expanded rapidly to accommodate larger quantities of data. New increments that were previously unheard of are now commonly found in external hard disk drives. Consult the following chart for a breakdown of capacities.

Unit Name





8 bits



1 thousand bytes



1 million bytes



1 billion bytes



1 trillion bytes



1 quadrillion bytes



1 quintillion bytes



1 sextillion bytes



1 septillion bytes

The amount of storage space that a user needs truly depends on the type of files that need to be saved. Options for HDD capacity range from less than 100 GB to more than 8 TB. Typical business documents, such as spreadsheets, databases, and written works, can be saved on smaller drives. A document created in Microsoft Word 2010, containing one character, takes about 13 KB (primarily because of paragraph styles and other auto-formatting contained within the programme).

However, audio files and high-resolution graphics such as photos and videos take up a great deal of memory; in this case, a larger drive is ideal. A movie recorded in HD can take up to 6 GB or more of space. A good rule of thumb to follow is to buy more space than may be needed at the current time to accommodate further accumulation of data. This prevents one having to buy another, larger external HDD should the current one fill up.

External Hard Disk Drive Interfaces

The interface is the method of data transfer from the peripheral hard drive to the main computer. The most common interface is through a USB port. Other common interfaces include FireWire, SATA, SCSI, and SAS. These interfaces vary in speed, with USB 3.0 being faster than previous generations of USB and other interfaces outdoing USB. The primary consideration when choosing an interface is being sure that it is compatible with the computer. For example, not all PCs work with FireWire.

Where to Find External Hard Disk Drives

You can find external HDDs at a variety of retailers, including office supply shops, electronics shops, appliance shops, and department stores. Because some heavy-duty computer users frequently upgrade their devices, you may be able to find used HDDs through classified adverts and online auctions. Just be sure that such a drive has been completely wiped of all the previous owner's files and information.

How to Find an External Hard Disk Drive on eBay

Finding an external HDD on eBay is a breeze. You can start by performing a keyword or keyphrase search. This method allows you to view all pertinent listings throughout eBay, regardless of categorical location. At the homepage, locate the search field and type in your chosen word or words. For example, you might start with a basic term, such as 'external hard drive', or if you have certain criteria in mind, you can get specific by adding a storage capacity, brand name, and so forth. Next, click the Search button. You can then see all HDDs that are listed within the site. From here, you can start viewing individual listings, or you can select a specific category to look at products in that are in one group.

You may find that external HDDs show up mostly in one particular category, even though there may be scattered listings in other categories as well. If this is the case, or if you want to browse for other computer peripherals as well, you can navigate through the directory. To do so, return to the homepage and find the link for all categories. Click this, and then find the name of the category that you saw during the keyword search.

Whether you use the keyword or directory method of browsing, you can make use of category filters to filter listings based on certain criteria, which helps you to narrow down your options even further.


An external hard disk drive is a worthwhile investment for anyone who is interested in adding more storage space to a computer so that it can handle large files and big data backups at the same. A hard disk drive (HDD) differs from a solid-state drive (SSD) in that it uses moving parts to read and write data. For this reason, an HDD is a bit more delicate than an SSD, but HDDs are generally cheaper than SSDs.

Consumers should decide first whether they need a portable or desktop HDD. A portable version usually has a smaller form factor and storage capacity but can be powered through the PC's USB port. A desktop HDD is a larger unit that requires an AC power source in addition to USB connectivity. Once this decision has been made, the consumer should figure out how much storage capacity is required, as well as what type of interface is compatible with the PC and offers a satisfactory data-transfer rate. Computer users should remember to buy more storage space than they think they will need. By taking all of these factors into consideration, anyone can buy an external HDD for backing up or storing vital data.

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