Computer Storage Devices

8 min readOct 11, 2021

Storage devices can be referred to as hardware connected to a computer or server whose primary purpose is to store data. These are connected to computers externally or internally and are used to store data temporarily or permanently in this form.

As mentioned above, computer storage devices can be classified according to how the data is stored temporarily or permanently and whether it is directly or indirectly connected to the central processing unit. They can be identified as primary storage, secondary storage, tertiary storage and offline storage.

Primary storage

Primary storage also known as main memory, internal memory, prime memory is the only one directly accessible to the CPU .

Ex: — RAM, ROM, Cache

RAM

Random access memory is where data is temporarily stored until it is processed. This is called volatile memory because the data is erased when the computer does not have power. RAM has both abilities to read and write. RAM can be seen in two main forms: DRAM and SRAM

SRAM

Not need to be refreshing

Faster performance

Expensive

More power consumption

Present in cache memory

DRAM

Need a regular refreshing to update data

Slower performance

Less expensive

Less power consumption

Present in main memory

ROM

This is a non-volatile memory as data is not erased in the power off. This memory, which stores basic input output system commands (BIOS), is mounted on the computer’s motherboard. Masked ROM, Programmable ROM, Erasable and Programmable ROM, Electrically Erasable and Programmable ROM, Flash ROM are types of ROM.

Cache memory

Cache memory called central processing unit memory, retains frequently used data and acts as an intermediary between the CPU and the primary memory. As a result, the CPU speed increases. And also cache memory is a volatile memory.

Ex: -Level 1 cache, Level 2 cache, Level 3 cache

Secondary storage

Secondary storage is known as the backup memory, additional memory and auxiliary memory. This memory, which stores data and information permanently, is called non-volatile memory because its data is not erased even in the absence of electricity. Like primary memory, secondary memory is not directly connected to the CPU.

The way data is stored in this memory can be discussed under three main sections.

· Magnetic media devices ex: — Hard disk, Floppy disk, Magnetic tape

·Optical media devices ex; — CD, DVD, Bu-ray

· Solid state devices ex: — USB flash drive, memory card

Basis

Size — Primary memory is smaller than secondary memory

Data storage — Primary memory storage data temporary but secondary memory storage permanently.

Location — Primary memory is internal devices ,secondary memory is internal or external devices.

Tertiary storage

Tertiary storage is also known as nearline storage because it is near to online. Typically, it involves a robotic mechanism which will mount and dismount removable mass storage media into a storage device according to the system’s demands; such data are often copied to secondary storage before use. It is mostly not a part of personal computers and doesn’t need human intervention and has automatic functioning.

Ex: Magnetic tape, optical disc .

Offline storage

Offline storage is any storage that is not currently online, live or connected to the computer. Data from an offline storage is stored permanently even when disconnected from a computer. This device must be reconnected by the human operator when connected. Offline storage is generally portable in nature and can be used on different computer systems .

Ex: — Memory card, floppy disk, USB flash drive, Compact disk

………..Magnetic storage devices…….

Data is stored in this storage medium by generating a magnetic charge. And, these are quite common in all the systems now as they are affordable and easily accessible.

Floppy disk — It is used in personal computer and is portable. It was introduced by IBM IN 1969. Floppy disks have less storage capacity and are less expensive. It can store data up to 1.44MB. It can see two sizes 5 ¼” and 3 ¼”. This is almost never used today.

Zip diskette — Zip disk was developed by ‘Lomega’ Company. It was advance than floppy disk and used as secondary storage. It can hold up to 100MB or 250MB of data

Magnetic tapes — Magnetic tape was introduced by Fritz Pfleumer in 1928. In the early day this was used to record sound. Today it is replaced by CD, DVD

Super disk — Super disk was introduced by Imation Organization. Super disk was popular with OEM computers and has capable of 120MB storage.

Hard drive — Hard drive also called hard disk drive. It is more popular media to data store. This device, which is found inside the computer can also be connected externally to the computer. This is called read and write memory as it allows the user to read data as well as

write new data. Capacity is between 250GB and 4TB

Internal hard disk is faster and less expensive than external hard disk.

External hard disk is portable and small size than internal hard disk.

Magnetic storage devices

Advantages……

Access and recovery time is fast

Cheap per unit of storage

Disadvantages…..

Can be easily damage

Eventually break over time

………Optical storage devices……..

These devices use lasers and lights to deal with data. They are cheaper than flash devices and can sore more data as well.

CD-ROM — The data here can only be used for reading Ensure data security

CD-R — After writing data only once, it can only be used for reading

CD-RW — Ability to rewrite data

size- 650–900MB

DVD-ROM — This is also used to read only. It can store up to seven times the amount of data stored on a CD. Ensure high quality video and audio data storage.

DVD-R — After writing data only once, it can only be used for reading

DVD-RW — Ability to rewrite data

size- 4.7–9.4MB

Blue-ray Disc(Recordable) — After writing data only once, it can only be used for reading. This mainly used to store high definition video(HD)

Blu-ray RE(Recordable Erasable) — In addition to the written data, repeated data can be added.

Blue-ray 3D — Used to record 3D video.

size- 25–128BG

Optical media devices

Advantages….

Mass storage capacity

Long media life

Disadvantages…..

Not cheap if terabytes need to be stored

Not as portable as flash media

………..Flash storage devices………..

It is widely used as a substitute for magnetic and optical storage devices. They are affordable, portable, and accessible. Therefore, the use of flash storage devices has become popular. Flash memory was invented Toshiba in 1980. Flash memory is also known as electronically erasable programmable read only memory (EEPROM) .It is also non-volatile memory.

USB Flash Drive — USB flash drive is also called USB thumb drive, pen drive, USB stick. It is light and portable. It plugs into USB port of the computer. USB flash drive can see available in sizes such as 2GB,4GB and up to 256GB. This has become safe and more popular way to store and transfer information

Memory card — It is also called flash memory card and store data such as image, text, video. Memory card is mostly used into smart phone, digital camcorder, handheld computer, MP3 players and more.

SSD — SSD stands for ‘solid state drive’. It is a non-volatile memory and store any type data. SSD is lower power consumption, faster access time and noiseless operation. It has 120GB to 30.72TBcapacities.

SD Card — SD card is also known as Secure Digital memory card. This is used to store data in the camera and phones. SD card was designed by Panasonic, Toshiba, and SanDisk in 1999. This storage device has a capacity ranging from 2GB to 128TB

Multi-media card — It is called MMC. It is small type of memory card. It is used into portable devices like as PCs, smart phones, car navigation, music media player. It capacity is up to 512GB.

Flash storage devices

Advantages…….

Smaller size

Portability

Low chances to damage

Save all data when power off

High speed

Disadvantages…….

It is more costly than hard disk

Easy to lose due to its smaller size

It hasn’t any write-protection mechanism

Flash memory contains a limited number of write and erases cycles before failing

Erasing is more costly

Online cloud storage devices

Cloud storage is mainly on the internet in the form of data bases and files. This makes the data available anywhere and anytime. This is very famous in today’s world as the data is remotely accessible on the network. Some of the most popular cloud storage providers are Apple(iCloud), Amazon , Dropbox and Google.

Characteristics of computer storage devices

Ø Storage devices allow easy transfer of data from one device to another.

Ø Saving and replacing the data is easier.

Ø They are easily accessible and very convenient to use by anyone.

Ø Their capacity is increasing with the time

Ø They are readable, editable, and re-editable allowing easy replacement of data.

In past floppy disks, zip disks, punch card were used mostly. But at present flash memory and optical disc used mostly. Really, they are easy to use. The main reason for that their sizes and capacity.