Which of the following is an example of why hard disks are so popular?

Hard disks have been the dominant form of computer data storage since the 1960s. There are several key reasons why hard disks became so popular and remain a critical component of most computing systems today:

High storage capacity

One of the main appeals of hard disks is their ability to store very large amounts of data in a small form factor. The first commercial hard disk released in 1956 by IBM could store a remarkable 5 MB of data. Fast forward to today, and consumer hard drives are available with capacities up to 16 TB. This vast storage potential enables users to keep all their software, media files, documents, and more on a single drive.

Low cost per gigabyte

Hard disk drives provide an extremely low cost per gigabyte compared to other data storage mediums. Although the price of HDDs has fluctuated over the decades, it has reliably remained affordable for average consumers. Today, the cost per gigabyte for a typical hard drive is around $0.02 to $0.03. This makes HDDs ideal for cost-effective, high-capacity storage, both for personal use and in data centers.

Non-volatile storage

Hard disks retain data even when powered off, known as non-volatile storage. This is a vital capability that allows permanent data storage. When the system is turned off, the hard drive maintains the binary code that constitutes the files stored on it. When powered back on, access to that encoded data remains intact. This non-volatile nature is essential for most computing purposes, differentiating hard drives from temporary storage mediums like RAM.

Mechanical reliability

The mechanical design used by hard disk drives to read/write data has proven highly reliable over decades of use. HDDs utilize rotating magnetic platters that spin at high speeds, along with read/write heads that access precise sectors on the disk surfaces. This electromechanical approach delivers consistent performance for both random and sequential data access. The mean time between failures (MTBF) for today’s hard drives is typically 1 to 1.5 million hours under normal operating conditions.

Data transfer speed

Although their data transfer rate has been surpassed by SSDs in recent years, HDDs are still reasonably fast. The first hard disks had data transfer speeds around 10 kB/s, while modern HDDs can achieve up to ~200 MB/s for sequential reads/writes. This provides adequate speed for most common workloads like operating systems, applications, media playback, file transfers, and more. Their higher latency for random accesses is also reasonable for many use cases.

Established technology

Hard disk tech has been refined for over six decades since the IBM RAMAC system. This has enabled manufacturers to develop very advanced and competitive HDD designs. The widespread success of hard drives further incentivizes continued innovation from major players like Seagate, Western Digital, and Toshiba. The maturity of HDDs lowers costs and risks for PC builders and data center operators who rely on proven, reliable technology.

Evolution of Hard Disk Capacity

One of the key measures of hard disk progression is the increasing storage capacity over time. Some major milestones include:

1956 IBM 350 RAMAC – 5 MB
1962 IBM 1311 – 2.6 GB
1980 Seagate ST-506 – 5 MB
1981 IBM 3380 – 317.5 MB
1988 PrairieTek 220 – 2 GB
1991 IBM 0663 Corsair – 1 GB
1997 IBM Deskstar 16GP Titan – 16.8 GB
2002 Maxtor MaXLine III – 300 GB
2005 Hitachi Deskstar 7K500 – 500 GB
2009 Seagate Barracuda XT – 2 TB
2011 Seagate Barracuda – 3 TB
2013 Western Digital WD Black – 4 TB
2015 Seagate Archive HDD v2 – 8 TB
2019 Western Digital Red – 16 TB

This demonstrates the tremendous progress, from only megabytes initially to multiple terabytes today. Hard disk storage capacities have historically doubled roughly every 2 years, although growth rates have slowed recently. This is still an exponential curve enabled by innovations like perpendicular recording, shingled magnetic recording, helium-sealed platters, and more advanced read/write heads.

HDD densities continue improving, suggesting capacities may reach ~30-50 TB in consumer drives and ~100 TB in data center drives in the next several years. However, limitations from superparamagnetism and physical bit sizes will present challenges for much further growth using current technologies. Bit patterned media has been proposed to push densities even higher moving forward.

Cost per Gigabyte Trends

In addition to higher absolute capacities, hard disk drives have also delivered substantially lower costs per gigabyte over time. Some approximate HDD costs per gigabyte include:

1983 $10,000
1984 $5,000
1990 $500
1995 $200
2000 $1
2005 $0.33
2010 $0.07
2015 $0.03
2020 $0.02

This massive reduction in cost per gigabyte is driven largely by economy of scale and improving production efficiencies. As HDD technology matured and production volumes increased, costs dropped precipitously – providing exceptional value for money. While SSDs have lower cost per gigabyte today, HDDs continue offering more storage capacity for the price which keeps demand high.

Various forecasts predict the hard disk cost per gigabyte declining further in the coming years, potentially reaching around $0.008-$0.015 per gigabyte by 2025. However, commoditization effects and rising SSD competition may slow the pace of price drops compared to historical levels. Overall HDD costs should remain low enough to make them viable for very large and cost-sensitive storage needs.

Advantages of Hard Disk Drives

Some of the main benefits that HDDs provide, which have driven their widespread adoption, include:

Low Cost per Gigabyte

As already highlighted, HDDs offer unmatched storage capacity potential at very affordable prices, which continues declining over time. For cost-effective storage of large volumes of data, hard drives cannot be beaten. This makes them ideal for average consumers and businesses seeking huge capacities without big budgets.

Proven Reliability

Hard disk drive designs have been refined for decades into very dependable and resilient storage systems. Their mechanical operation meets stringent reliability, availability, and serviceability (RAS) requirements for personal computers and enterprise storage. HDD failure rates are low enough for practical storage uses.

High Data Throughput

The speed of sequential data transfers on modern HDDs is sufficient for many common workloads. Sustained transfer rates up to ~200 MB/s help enable quick loading of programs, files, media, and other content. Performance is further boosted by caching and buffering techniques for frequently accessed data.

Non-Volatile Storage

The non-volatile nature of hard drives enables permanent and dependable data storage. The encoded data remains intact on HDD platters whether powered on or off. This critical trait makes hard drives suitable as long-term data repositories.

Large Capacities

HDD designs allow incredibly high storage densities in relatively compact devices. Consumers can choose drives up to ~16 TB for desktop PCs and NAS use. Data centers employ drives up to ~20 TB for massive distributed storage needs. These huge capacities provide ample space for archival data.

Shock Tolerance

Hard disk drives are engineered to withstand moderate shocks and vibration that occur in desktop computers or servers. This is enabled by head parking, gyroscopic forces in the spinning platters, and shock absorbing mounts. HDDs will survive typical bumps, drops, and impacts when installed properly.

Disadvantages of Hard Disk Drives

While HDDs have proven very capable for general storage purposes, they do carry some inherent downsides, such as:

Relatively Slow Random Access

The mechanical nature of hard drives typically makes them slower at reading/writing small random blocks of data across fragmented files. Their random access time is generally in the 2-10 ms range, compared to <0.1 ms for SSDs. This makes HDDs less suitable in latency-sensitive uses.

Susceptibility to Magnetism

Being based on magnetic storage principles, hard disk drives are vulnerable to data corruption or damage when exposed to strong magnetic fields. Users must avoid close proximity to magnets which can erase data on platter surfaces.

Audible Noise

The spinning platters and moving heads in HDDs generate audible noise during operation, similar to a quiet electric motor. While not very loud, this may be distracting for some users. SSDs are effectively silent since they contain no moving parts.

Higher Power Consumption

Hard drives consume more power overall than SSDs due to the energy required to rotate platters and move heads. Typical HDD power needs are 5-10 Watts, reducing battery runtimes in notebook computers. SSD power use is closer to 2-3 Watts.

Heavier and Larger

Even compact 2.5″ hard drives weigh around 100-150 grams. This makes them less ideal for light and thin mobile devices. SSDs are lighter at about 30-60 grams for typical 2.5″ drives. 3.5″ desktop HDDs also require considerable space which limits design flexibility.

Susceptibility to Shock Damage

Although engineered for resilience, HDDs can still incur catastrophic failure if subjected to excessive shocks beyond their design limits. Dropping a hard drive can potentially damage internal components and render stored data unrecoverable. SSDs are inherently better suited to harsh environments.

Uses Cases and Applications

Some of the most common applications where hard disk drives are utilized include:

Desktop PCs

The majority of desktop computers are built using at least one internal HDD for the operating system and data storage. Multiple hard drives can be installed for very large capacities. Standard 3.5″ HDDs mount conveniently into desktop drive bays.

Notebook Computers

Most laptops employ a 2.5″ HDD as the primary storage device. Smaller form factor hard drives allow mobility while still delivering ample capacity. Some newer notebooks are transitioning to sole SSDs, but many still include HDDs.

Game Consoles

Gaming consoles traditionally relied on 2.5″ hard drives for game storage and save data. For example, the PlayStation 4 used interchangeable HDDs to augment the limited built-in flash storage. High capacities at low cost make HDDs practical for consoles.

External Storage

External USB hard drives are widely used for backup, secondary storage, and data portability. These portable HDDs just require connection to a host device to access extra storage capacity. Their affordability makes external HDDs accessible to home users.

NAS Devices

Network-attached storage systems commonly populate multiple internal drive bays with high-capacity HDDs. This enables economical bulk data storage that can be accessed and shared over a local network. HDD reliability allows continuous NAS operation.

Data Centers

Large-scale data centers employ specialized enterprise-class 3.5″ HDDs to build out massive storage infrastructure for cloud services and networks. The low cost per terabyte makes HDDs ideal for petabyte-scale storage farms. Fast interfaces like SAS are used.

Surveillance DVRs

Digital video recorders designed for continuous security camera footage storage often utilize internal hard drives. High-capacity HDDs can economically ingest large amounts of constant video feeds that must be retained and accessed later.

Media Servers

Home theater PCs, streaming boxes, DVRs, and media servers leverage internal HDDs to conveniently store large collections of movies, music, and recorded television programming for on-demand playback and distribution throughout the home.

Game Consoles

Dedicated gaming consoles like the PlayStation 4 historically used 2.5″ hard drives for game storage and save data. The low cost per gigabyte makes HDDs practical for consoles, while still providing ample capacity for games.

The Future of Hard Disk Drives

While growing SSD adoption is impacting the HDD market, hard drives are expected to retain relevance for years to come especially in areas like:

High-Capacity Storage

Hard drives will continue satisfying needs for affordable, high-density storage with multi-terabyte capacities. Where massive storage is required, HDDs hold a substantial per-gigabyte cost advantage over SSDs.

Bulk Archive Systems

Archival storage and backups with relaxed performance requirements can leverage HDDs for maximum capacity at a low price point. This fits well with nearline HDDs for data center storage tiers.

Cold Data Storage

Rarely accessed “cold” data can be moved to dense HDDs for cost-efficient bulk storage. As hot data shifts to speedier media like SSDs, HDDs still carry substantial cold storage value.

Lower-Cost PCs

Budget desktops and laptops will continue utilizing HDD technology to meet capacity needs while minimizing costs. For non-performance oriented systems, HDDs easily satisfy basic storage demands.

High-Density Servers

Large-scale data center servers designed for mass storage can pack many high-capacity HDDs into single dense enclosures. These high-density servers are ideal for unstructured data growth.

Hard disk vendors continue advancing HDD technology for higher capacities, improved reliability, and better performance. Platforms like sealed Helium drives, shingled recording, microwave assisted magnetic recording, and heat-assisted magnetic recording help push HDD capabilities further while keeping costs relatively low. Hard drives still have an extensive role to play as a high-value storage medium.


In summary, hard disk drives became the dominant form of computer storage over decades thanks to a compelling combination of performance, capacity, capabilities, affordability, and widespread adoption. As an established and mature technology, HDDs deliver huge, reliable storage potential at very reasonable costs which remains highly appealing for personal computing and large-scale data storage needs. While SSDs are now preferred for many applications requiring faster access or compact form factors, hard drives retain advantages in costs, capacity, and time-proven designs that ensure HDDs will continue serving critical storage roles into the foreseeable future.