Buying an Internal Hard Disk Drive to Replace a Damaged Drive

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Buying an Internal Hard Disk Drive to Replace a Damaged Drive

One of the most important functions of a computer is data storage. The options available for storing data have increased in capacity, and decreased in size, dramatically over the past few decades. Hard disk drives are the most common type of computer storage used on modern computers. Today's hard drives can each store the data equivalent of millions of punched cards, the data storage medium of the 1930s. They do this in a package smaller than the size of a small book.

Besides storing data, internal hard drives usually store the "operating system" of a computer. This is the software that manages a computer's hardware and provides common services for computer programmes. Buyers looking for internal hard disk drives should know what the different types of hard disk drives are. They should also understand how the different features of a hard drive affect its performance and characteristics. Finally, they should know where to find a hard disk drive, and how to purchase it.

How Internal Hard Disk Drives Work

Hard disk drives (HDDs) use many discs coated with magnetic material to store data. These discs, also called "platters", spin at very high speeds. The platters are rigid, hence the "hard" in "hard disk drive". Magnetic heads, attached to a moving arm, are positioned above each platter. Data is read from, and written to, the platters by these magnetic heads. The moving arm allows the heads to reach any part of the spinning disc below it. The design of hard disk drives has not changed much since IBM introduced the first HDD was introduced in 1956, but continuous improvements have reduced the physical size of hard disk drives while increasing their storage capacity.

The Two Types of Hard Disk Drive Interfaces

There are two common standards used to connect an internal hard disk drive to a computer. The newer standard, SATA, brings new features and faster data throughput as compared to the older PATA standard. When replacing a damaged hard disk drive, users can quickly identify the type of interface used by looking at the cable connecting the drive to the motherboard (this is different from the cable connecting the drive to the power supply).

PATA Interface

The PATA interface, also called "IDE", or simply ATA, was the primary hard disk drive interface before the introduction of the SATA interface in 2003. Some older computers still use PATA hard disk drives and interfaces. The PATA (Parallel ATA) interface uses 40 pins to connect the hard drive to the computer. Up to two drives can be connected to the motherboard using one cable. Some motherboards were made with up to three or four PATA interfaces, allowing users to connect six or eight hard drives respectively.

After the introduction of SATA, the use of PATA interfaces declined. Motherboards made after the introduction of SATA usually have one PATA interface and several SATA interfaces. The presence of PATA interfaces in modern motherboards is being phased out.

SATA Interface

The SATA interface is an abbreviation for "Serial ATA". Similar to the older PATA interface, SATA can be used to connect hard disk drives and other storage media like optical drives. SATA is capable of much faster data throughput, up to 6 Gbit/s for SATA revision 3.0 interfaces.

SATA Revision

Maximum Throughput


Revision 1.0a, or SATA 1.5 Gbit/s


Revision 2.0, or SATA 3 Gbit/s


Revision 3.0, or SATA 6 Gbit/s


Revision 3.1


Revision 3.2 or SATA Express

8 or 16

The SATA interface uses a cable that is much smaller than PATA's ribbon cables. One cable can be used to connect only one drive to one SATA interface on the motherboard. SATA interfaces are backward and forward compatible. For example, a SATA 3 Gbit/s drive can be used with a SATA 1.5 Gbit/s motherboard. However, data transfer speeds are limited to the lower speed, in this case, 1.5 Gbit/s.

The Physical Size of a Hard Drive

Hard disk drives come in two standard sizes, one that is commonly used in desktop computers, and another that is used in laptops. This is also known as the "form factor" of the drive. Laptop drives are smaller in size (2.5 inches compared to 3.5 inches for desktop drives). It is not possible to fit a desktop drive into a laptop. However, a laptop drive can be used in a desktop by using an adapter to increase the size of the drive, allowing it to fit a standard hard drive slot.

Other Factors to Consider When Choosing a Replacement Hard Drive

When replacing a damaged drive, buyers must choose a new hard drive that matches the interface, and the form factor of the old drive. However, there are several other factors to consider, and buyers can easily replace the damaged drive with a better performing replacement.

Storage Capacity

The storage capacity of a hard drive is one of the most important factors when choosing a drive. Simply put, the higher the capacity, the more data can be stored on a hard drive. Modern hard drives can store up to several terabytes (TB) of data. However, modern storage requirements are also large, with many users needing space to store large image, sound, and video files.

The actual capacity of a hard drive is slightly less than what is stated. This is because of the way many manufacturers measure storage. Operating systems measure storage in multiples of 1024. One megabyte (MB) consists of 1024 kilobytes (KB), and 1024 MBs make one gigabyte (GB). However, manufacturers use multiples of 1000. As a result, a hard drive that a manufacturer states is 320 GB in size is counted as a hard drive with about 300 GB by the operating system. This is normal and not a cause for concern.

Hard Disk Cache

Also called the "buffer memory", a hard disk's cache is the embedded, high speed memory in a hard drive. This acts as a buffer between the computer and the physical hard disk platter. Manufacturers sometimes sell the same hard drive with different cache sizes, the drive with more cache being more expensive. In general, more cache is useful when working with large files.

The Spin Rate of the Drive

Hard disk drives use spinning platters to store data. The speed at which these platters rotate is directly related to how fast data can be written and read by the drive. Some common spin rates are 5400 RPM, 7200 RPM, 10,000 RPM, and 15,000 RPM. The lower speed 5400 RPM drives are commonly used in laptops because of lower power consumption. The very high speed 15,000 RPM drives are mostly used on servers. In general, drives with faster spin rates can read and write data faster. However, other factors (such as areal density) also affect how fast data can be transferred.

Seek Time

The seek time of a hard drive is defined as time taken for the head assembly to move to the track on a disk where data is read or written. The first hard drives had a seek time of around 600 milliseconds (ms), but modern hard drives are much faster, with seek times as low as 4 ms on server hard drives, and averaging 9 ms for desktop hard drives.

Audible Noise

The audible noise of a hard drive (and other electronic devices) is measured in dBA. Hard drives are not very loud when used individually. However, if a computer uses several internal hard drives, noise levels can rise to uncomfortable levels. Low noise disks use fluid bearings, slow spin rates, and reduced seek speeds to minimise noise. Smaller form factor drives are also generally quieter than larger ones. In general, quieter operation results in reduced seek performance.

Finding Internal Hard Disk Drives on eBay

Buyers looking for internal hard disk drives online can choose from a diverse range on eBay. Buyers can quickly locate the right type of hard disk by running a quick search from the search bar on eBay' s home page. If the resulting list is too long, it can be narrowed down by entering more specific keywords. For example, a search for "7200 RPM laptop hard drive&" lists fewer results than a search for "laptop hard drive&". However, the results are more relevant. The list can be whittled down further by choosing from different criteria including brand, storage capacity, and interface of the drive.

Buyers should take the time to review a seller's return and exchange policy before committing to a purchase. As with any electronic device, there is a chance that the purchased hard drive is defective and needs to be returned. If this information is not available on the item's page, buyers can ask seller's for it directly.


Internal hard disk drives are one of the most common devices used for storing data on computers. They are called hard disk drives because data is stored on rigid, or "hard", discs coated with magnetic material. The basic elements of hard disk drives have not changed much since the first hard drive was introduced in 1956. However, many improvements have dramatically increased data storage capacity while decreasing the physical size of hard drives.

Hard drives come in two common form factors: 2.5 inches for laptops, and 3.5 inches for desktops. There are two different types of interfaces used to connect hard drives to computers: SATA and PATA. When replacing a hard drive, buyers should purchase a drive that matches the form factor and interface of the drive they are replacing. Other factors buyers should consider include the drive's capacity, spin rate, seek speed, and cache size. Buyers looking for internal hard disk drives online can choose from a wide range of hard drives on eBay.

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