Computers utilize a variety of storage devices and media in order to read and write data. Without permanent or temporary storage, a computer wouldn’t function as expected.
Most machines would be completely useless without a place to store digital data. Everything from the operating system to programs and individual files exist on storage after all.
The early days of computer memory featured magnetic tape and floppy disks. Now things like hard drives, solid state drives, cloud storage services etc are used more often.
In general, storage device types can be separated into two broad categories:
Nearly a dozen types of permanent storage are available for computers. On the other hand, temporary memory is often limited to Random Access Memory (RAM) and cache memory.
Each type of storage or memory comes with its own benefits and disadvantages. It’s important to understand what options are available on the market today and decide which solutions make sense for a given computer.
Consider the following storage devices used in computer systems starting from permanent storage devices:
Types of Permanent Storage Devices
Magnetic Storage Types
1. Hard Disk Drive
A hard disk drive (HDD) is a non-volatile storage medium. Non-volatile data remains on a given device unless rewritten or deleted.
In hard drives, an electromagnet creates positive or negative charges on the disk surface. The charges create binary code read as the rotating disk and actuator arm work in conjunction.
Data is read along concentric circles, known as tracks, and sectors, known as wedges. Currently, hard disks remain in regular use but their popularity is diminishing.
HDDs come with a variety of benefits, including high storage capacities and overall low cost, that’s why they are mostly used for backup and archiving purposes.
Alternative forms of storage often cost more for similar storage capacities. These days, a two-terabyte hard drive might cost $50.00 or less.
Hard drives include mechanical parts, though, so they wear down over time and are susceptible to sudden data loss from impact damage. Many hard drives feature fast read/write speeds, but other faster storage types are available today.
Mechanical HDDs have a rotating head, that is why you will see specs like 7.5K RPM or 10K RPM (Revolutions Per Minute) on HDD devices.
Typical Storage Capacity: 500 GB to 4+ TB
2. Magnetic Tape Device
The Eckert-Mauchly UNIVAC I system originally used magnetic storage device tapes back in 1951. Surprisingly enough, magnetic tape is still used today and sees regular improvements.
Data is written onto magnetic tape through various means, which is outside the scope of this description.
It’s possible to write data onto magnetic tape along its length or width, though. At this point, magnetic tape is used in academic fields and countless other situations such as backup storage systems. Specialized equipment is required to read magnetic tape.
For ordinary consumers, magnetic tape might seem like an outdated technology. Researchers continue to develop magnetic tape for commercial use.
Tape features higher storage capacities than hard drives, and they’re more reliable than HDDs.
They feature a similar overall cost compared to similar hard disks as well. In fact, some analysts predict that the use of magnetic tape will continue to grow and expand. Tape could replace hard drives in commercial settings moving forward.
3. Floppy Disks
Generally speaking, floppy disks existed as storage devices from 1971 to 1999. The disk drives required to read floppy disks are no longer included in mainstream computers.
Finding a working floppy disk drive outside of industrial settings can prove challenging in some cases.
Nonetheless, floppy disks relied on a magnetic disk that could be read and written via read/write heads. Various motors and the floppy disk drive are required in order to access data on floppy disks.
In the past, floppy disks came with the benefit of being affordable and relatively fast. They supplemented a computer’s main storage device well and usually they were used to boot-up a computer (e.g older computers using MSDOS operating system could boot-up using a floppy disk).
Most floppy disks held less than two megabytes of data. Unfortunately, floppy disks maxed out at 240 MB of storage space.
Although floppy disks are used in industrial settings, consumers often consider them extinct and obsolete compared to hard drives. Floppy disks were manufactured in various sizes over the years.
Flash Storage Types
4. SSD (Solid State Drive)
Solid state drives rely upon NAND flash memory to deliver blistering read/write speeds. Transistors are wired in series on a given circuit board, meaning SSDs lack moving parts. For that reason, data can be accessed immediately and without much noise or heat.
A computer’s operating system accesses the storage drive, and SSDs come in both internal and external configurations. Faster read/write speeds lead to better load times, a faster operating system, and other benefits.
Typically, SSDs cost more money than HDDs with similar storage capacities. They cannot be beaten on read/write speeds or longevity, though.
Solid State Drives degrade in memory quality over millions of write operations, but they’re not susceptible to damage like hard drives.
Plus, they’re quieter than hard drives and come in smaller form factors. Portable devices achieve better battery life due to the non-mechanical function, which is always a desirable result.
Typical Storage Capacity: 120 GB to 1+ TB
5. USB Flash Drive
Like SSDs, USB Flash Drives rely upon NAND flash memory. These devices are designed to be portable, pocketable storage solutions.
They plug into a computer’s USB port and feature fast read/write speeds. In simple terms, flash drives are best used as ultraportable storage devices.
Flash drives provide an excellent solution for moving files from one device to another quickly. They’re often used as backup devices for large amounts of data as well.
The benefits of USB flash drives speak for themselves. These devices are extremely portable and feature no moving parts, so the data is secure.
Also, a variety of storage capacities are available on the market, although capacities over 256 GB are uncommon.
It doesn’t help that flash drives are expensive compared to HDDs, which feature much higher capacities at lower prices. Such memory sticks serve a variety of purposes, and it never hurts to keep one lying around.
Typical Storage Capacity: 8 GB to 256GB (Maximum 2 TB)
6. SD Card
SD Cards rely upon flash memory and are designed for portable devices such as cameras, smartphones etc. Most laptops and many smartphones feature SD Card readers.
For sizing options, manufacturers offer full-size SD, miniSD, and microSD cards with various capacities.
Full-size SD cards often slot into desktop PCs and laptops. Cameras and smartphones or tablets often accommodate miniSD or microSD cards.
SD cards are categorized by their read/write speed, which can vary 12.5 megabytes per second to 3,938 MB/s.
Like USB flash drives, SD Cards are portable and easy to pocket. Smaller capacities are available at competitive pricing compared to flash drives and other memory.
They’re best used as portable device storage or for transferring files between devices. Otherwise, higher capacity cards cost a far more amount of money, and they’re not suitable for running programs or operating systems on computers. A better solution for portable devices and storage might not be available.
Typical Storage Capacity: 2 GB to 32 GB and Beyond
Optical Storage Types
Compact Disks (CDs) are known as optical storage devices. The disks feature microscopic pits and bumps that disk drives read as binary data.
While running in an optical disk drive, CDs rotate at a constant speed. A laser glides over the surface of the disk to read the binary data.
An optical lens reads this data and sends it to the computer or laptop being used. Depending on the disk type, CDs can be read only or read/write capable.
CDs typically contain audio and other small amounts of data. Storage capacity is limited to 700 MB, so they’re not suitable for high definition video storage.
Luckily, CDs cost very little money and take up very little space. They’re prone to scratches that render the disk unreadable, which leads to reliability problems.
Not all computers and laptops feature an optical disk drive today, either. Better disk-based storage options are available.
Typical Storage Capacity: 700 MB
Of course, DVDs look like CDs because they’re identical in size. All DVDs feature a spiral track with more data capacity than a CD, though.
The DVD drive utilizes a finer laser to read data due to the higher density. In essence, DVDs work exactly like CDs but with higher storage capacities. Dual layering is a process with DVDs that further increases storage capacity.
Large amounts of data, including standard definition video, can be stored on DVDs without a problem.
The average DVD features 4.7 GB of read/write data today. DVDs have been supplanted by BluRay Disks, so they’re often considered obsolete.
Regardless, DVDs are affordable and feature decent storage capacity. Computers from a decade ago typically featured a DVD drive by default. That’s not necessarily the case in 2020, so DVDs should be avoided unless absolutely necessary.
Typical Storage Capacity: 4.7 GB
9. BluRay Disks
The king of optical storage is the BluRay Disk. Once again, BluRay disks look like a standard CD or DVD. Even more data is packed into the spiral tracks of the disk.
An even more specialized violet laser reads the binary data on the disk’s surface. BluRay disks feature layering technology to increase capacity like DVDs.
With that in mind, a BluRay may feature storage capacity anywhere from 25 GB to 128 GB although the most popular capacity sizes are 25GB (single layer) or 50GB (double layer).
BluRay disks cost more than CDs and DVDs but should be considered the gold standard of optical media.
Multiple high definition movies and other data can be loaded onto a BluRay. Based on capacity alone, BluRay disks make more sense than other optical media solutions. BluRay disk drives don’t come standard on all computers, but they’re quite affordable to buy and install.
Typical Storage Capacity: 25 GB to 128 GB
10. Cloud Storage
Cloud Storage relies upon data stored on servers accessible at all times over the Internet.
Data might be stored on multiple servers to ensure 100% uptime and reliability. To access cloud storage, a computer needs access to the internet and a cloud storage provider.
Companies like Amazon, Google, and others offer cloud storage solutions. Data is always accessible and synced from the server to individual devices. Cloud data is essentially always available via the internet.
Since cloud storage is, in theory, always accessible, it’s convenient. A computer with an internet connection should be able to access data within seconds.
Location doesn’t matter with cloud storage, and a fast connection means instant access.
However, cloud storage is typically offered as a service and costs more money based on overall data storage needs.
Unavailable internet connections render cloud storage useless, and the overall security of such storage is sometimes questionable (although there are cloud storage services that offer encryption of data as well).
Types of Temporary Storage
11. RAM (Random Access Memory)
Unlike the previously covered storage devices, RAM is volatile data. Data stored in RAM is constantly cycled in and out and disappears after power is removed.
A computer’s CPU accesses RAM, which acts like a middleman between the CPU and non-volatile storage devices.
Otherwise, a computer would operate too slow for comfort by relying on non-volatile storage alone. Any data stored in RAM is available to the CPU in quick fashion, acting like the working memory for the CPU.
RAM directly affects the performance of a given computer. Most computers need 8 GB of RAM in order to function fast and smooth.
Sometimes, 16 GB or more is required for intensive use cases. RAM is quite expensive compared to other storage types but serves an invaluable purpose.
A quality RAM module leads to better PC performance and faster loading speeds in various applications.
12. ROM (Read Only Memory)
As the name suggests, this type of memory can only be read from the computer but you can’t write any data to it.
Another important characteristic is that ROM does not lose its data when the power is off (i.e it is non-volatile data).
ROM is usually used to store critical and essential data that helps to power-up a computer system and to perform an initial hardware test and setup. After the computer powers up, it starts using other types of storage such as hard disk, RAM etc.
An example of ROM is the BIOS of the computer (Basic Input Output System) which initializes the hardware and helps to start-up the whole computer system.
13. Cache Memory
CPUs feature cache memory embedded in the processing chip. Cache memory is faster than RAM but features much smaller storage capacity.
In a basic summary, such memory stores program instructions and similar data a CPU needs to access immediately.
This particular setup allows a computer to run faster and process tasks more efficiently. The cache memory handles the minute compute instructions in nanoseconds.
What Types of Storage Devices Are Commonly Used Today?
In today’s world, you’ll encounter certain storage devices more often than others.
RAM and cache memory comprise core parts of a computer. Solid state drives have started to replace hard drives in many computers due to speed and reliability.
On top of that, cloud storage continues to creep into the equation, especially for enterprise uses. Regular consumers still utilize USB drives and SD Cards for portability.
Conversely, floppy disks have all but died out except for extreme industrial use cases.
CDs and even DVDs remain rare in comparison to BluRay disks. Magnetic tape existed over 50 years ago but remains popular in academic and commercial settings.
More forms of storage devices are bound to pop up as time goes on. For now, manufacturers continue to develop and refine existing storage devices to increase capacity and reliability.
Primary Vs Secondary Storage Devices
All the devices explained above are some times categorized as Primary or Secondary storage devices. At a high-level, Temporary storage can be categorized as Primary Storage and Permanent storage can be categorized as Secondary Storage.
The table below summarizes the differences between Primary vs Secondary Storage Devices.
|Examples: RAM, ROM, Cache
|Examples: Hard Disk Drive (HDD), Solid Stade Drive (SSD), CD-Rom, DVD, Blu-Ray disks etc.
|Main memory in computers used to hold data that is currently in use.
|Long term storage to hold data and programs that might not be used currently but they can be used in the future.
|Provides the fastest data access in computers.
|Not as fast as Primary Storage.
|Located on the motherboard or on the CPU.
|Located on separate hardware storage devices.
|Data is usually lost (except ROM) when power is off.
|Data is not lost when power is off.
|Limited storage size.
|Larger storage size.
|Example Primary Storage Size (e.g RAM): 4GB to 128GB
|Example Secondary Storage Size: 512GB to 1TB