Computer Storage Devices
Weerasinghe S.A.
Faculty of Science, University of Kelaniya, Sri Lanka.
08/10/2021
Definition and the usage of computer storage devices
The need for computer storage devices is one of the major aspects of today’s computer world. The reason for this necessity is that a great deal of data is used for processing and this data and information are required to store for different purposes. Computer storage devices are the devices that are used to store data. Moreover, users of computers are given the accessibility of stored data by providing relevant instructions to the computers. The main purpose of using computer storage devices is to retain the data short-term or long-term. However, the usage of computer storage devices is not limited to this purpose. Some types of computer storage devices are widely used for protecting important data from frauds, disasters, and failures of computers or networks. There are different types of computer storage devices specified for several purposes. Therefore, the usage of computer storage devices is unbounded. The usage of them is depending on the categories of storage devices. All these types and usage of each storage device are reviewed in this article.
Types of storage
Computer storage can be divided into four main categories, such as,
1. Primary Storage (Main memory)
2. Secondary Storage
3. Tertiary Storage
4. Off-line Storage
Primary Storage (Main memory)
Primary storage, also known as the main memory, is one of the fundamental components of a computer system. Because the primary memory is accessible to the CPU of the computer directly. Therefore, Primary memory is involved in the functionalities of the computer system in several ways.
Primary storage can be divided into major three components, such as,
1. RAM — Random Access Memory
2. ROM — Read-Only Memory
3. Cache Memory
Each of these three types of primary storage has different features and they are used for different purposes.
(I Nyoman Gautama Satria Wibawa, 2015)
1. RAM — Random Access Memory
The main task of RAM is that to retain data temporarily until data is directed to the procedure of processing. The main aspect of RAM is that it is a volatile memory. It means that data retained in the RAM is removed from it when the power supply is off. In other words, when the computer system is turned off, the data stored in the RAM of this computer is lost. Moreover, directing processed information to output devices, or directing it to a secondary memory to store or to retrieving it from the secondary memory are done through the RAM of the computer.
According to some special characteristics, there are two types of RAMs used nowadays. These two types are called DRAM and SRAM. Both types are also volatile memory.
· DRAM
The acronym of DRAM is defined as “Dynamic Random-Access Memory”. DRAM is a standard computer memory that is created by mainly using capacitors and a few transistors. The data is allowed to store in a separate capacitor within a particular IC.
· SRAM
The acronym of SRAM is defined as “Static Random-Access Memory”. It is considered a semiconductor memory type. SRAM is used the six-transistor memory cell to store data. SRAM is mainly used as a cache memory for the CPU.
The main differences between SRAM and DRAM can be demonstrated in the below table.
2. ROM — Read Only Memory
ROM is non-volatile memory, which means that the data stored in the ROM are not lost when the computer is turned off. As the name of this storage implies, the content of ROM can only be read. In other words, the stored data in the ROM cannot be changed. ROM is contained Basic Input and Output System commands, also called “BIOS” stored by the computer manufacturing company.
(Jaiswal, 2021)
3. Cache Memory
Although smaller than the other types of primary storage, cache memory is faster than other types. The Cache memory is accessible to the CPU considerably quicker. Therefore, cache memory is sometimes called “CPU memory”. The main purpose of existing a cache memory is that to hold the data and programs that are frequently used by the CPU. Cache memory always acts as an intermediator between the CPU and the primary memory. Cache memory is also a volatile memory. Early years of the computer era, L1 (Level 1) cache memory was used. It was a small memory, which is ranges from 2KB to 64 KB. However, today’s modern computers are using L3 and L2 cache. The memory size of the L2 cache is range from 256 KB to 512 KB while L3 is range from 1 MB to 8 MB. (Jaiswal, Cache Memory, 2021)
Secondary Storage
Secondary Storage is used to store data and information permanently. However, secondary storage cannot be accessed directly by the CPU. Therefore, input and output channels of the computer are required to access them. In addition, the intermediate area in the primary storage is used to transfer the data stored in Secondary storage. There are internal and external secondary storage devices used now. The secondary storage devices are non-volatile memory. Hard disk is one of the most famous secondary storage devices. Further information about secondary storage devices is discussed in the next section of this article, “Types of Computer Storage Devices”.
Tertiary Storage
Tertiary storage is the third level storage that is generally used for storing a great amount of data safely for a long time. This type of storage device is usually having a considerably higher capacity. However, the speed of writing and reading of these storage devices is slower than the other devices. In other words, the speed of tertiary storage devices is identified as 5 to 60 seconds while secondary storage devices have high speeds such as 1 to 10 milliseconds. Therefore, tertiary storage devices are mainly used for storing archive data and information and accessed without human operators. Considering the technology behind the tertiary storage devices, according to the explanation of I Nyoman Gautama Satria Wibawa (2015), this type of storage devices contacts with the Robotic Mechanism. He explained that according to the demand of the system, it will mount and dismount removable mass storage media into a storage device. Magnetics tapes and optical discs and optical jukeboxes are the main examples of tertiary storage devices.
Off-line Storage
Off-line storage is called “disconnected storage”. The main feature of offline storage is that the inaccessibility of the stored data from a computer physically. It should be connected by a human operator before accessing again. Therefore, the privacy and confidentiality of the stored data and information are safe from computer-based attacks. In addition, offline storage devices cannot be controlled by the CPU. Moreover, this type of storage is used for transferring information, because the offline storage mediums are portable. Off-line storage is mainly used for increasing the protection of general information. For example, original data can be stored in an offline storage device, then it can be retained remote location physically. In case a disaster destroys everything that is stored in the main storage, this off-line storage can be used to recover it.
USB flash drives, memory cards, Floppy disks, Zip diskette are some examples of off-line storage. (I Nyoman Gautama Satria Wibawa, 2015)
Types of Computer Storage Devices
There are several types of computer devices used today. Each of these devices has its specific features. Therefore, each of them is used for specific purposes. These storage devices can be divided into the following categories.
Ø Magnetic Storage Devices
Ø Optical Storage Devices
Ø Flash Memory Devices
Ø Online cloud Storage Devices
Magnetic Storage Devices
Magnetic storage devices, also known as Magnetic Media Devices, use a magnetic field and magnetic charge for storing data in the device. Hard disk is the most popular magnetic storage device using these days. In addition, that, Floppy disks, and magnetic tapes are other examples of magnetic storage devices.
o Hard Disk
Hard disk is the major and the largest data storage device in a common computer.
The capacity of the modern Hard disk ranges from 160 GB to 2 TB. Moreover, the speed of a hard disk is measured by “rpm” ( Revolution per minute). The speed of a common hard disk using in the present is varying from 4500rpm to 7200 rpm. “millisecond” is the unit for hard disk access time. However, due to the rapid development of information technology, the above values can also be changed rapidly.(Cena, 2021)
Hard disk is constructed by combining basic components. These components and a brief introduction to each of these components are shown in the following table.
There are two types of hard disks used today. These are the internal hard disk and the external hard disk. Both types have many similar features. However, there are some main differences between these two types are indicated in the table below.
o Floppy Disk
The Floppy disk is a portable, soft magnetic disk. It is also considered as off-line storage. Floppy disk was one of the most popular storage mediums in the early years of the computer era. According to IBM, an estimated five billion floppy disks were sold per year globally, at the peak of selling in the mid-1990s. However, many high technically storage devices have been introduced to the world for the last decades. Therefore, floppy disks are obsolete now. However, it is used for storing archive data. 3 ½ and 5 ½ inches floppy disks were widely used. Floppy disks can store data up to 1.44MB. (IBM, 2011)
The following table indicates some key differences between hard disks and floppy disks.
o Magnetic tape
Magnetic tape is a magnetically coated plastic strip that can store data. Magnetic tapes are used as tertiary storage. The speed of reading and writing is considerably lower than the other storage mediums. However, Magnetic tapes are less expensive. Magnetic tapes are commonly used for backup.
Optical Storage Devices
Optical storage devices use a laser to store and retrieve data. Optical storage devices are popular since their portability, capacity, price, hierarchical- type file organization, and fast access time. Therefore, optical storage devices are widely used to store a large amount of information at a high-performance level in an efficient way. This is also tertiary storage. The most common types of optical storage devices are,
· CD-ROM
· CD-R
· CD-RW
· DVD- ROM
· DVD-R
· DVD-RW
· Blue-Ray R
· Blue-Ray RE
· Blue — Ray 3D
Flash Memory
USB flash drive is one of the most popular storage devices using in the present. It is very small, portable, and easy to handle. In addition, this is the easiest way to store and transfer data and information. It can plug into a USB port of a computer, then it functions as a portable hard drive. Flash drives are available in different storage capacities such as 2GB, 4GB, and up to 256GB. USB flash drive is one of the off-line storages. Moreover, it is called a solid-state device since it does not contain any moving parts. Therefore, flash memory devices are durable. There is not any physical part required to operate the flash memory. Therefore, the energy consumption of flash memory devices is considerably lower than other storage devices. The demand for flash memory is significantly increasing due to these advantages.
Online Cloud Storage Devices
Online cloud storage is a new concept which popularity is significantly increasing nowadays. The main feature of this technology is that users can upload their files to the cloud, and then they can access these files from any device and any location. (Shan-Hua Zou; Ning-Sheng Fang; Wei-Jie Gao, 2020)
In another word, data and information can be stored on the internet. However, a cloud computing provider is needed for this task. The cloud computing provider manages and operates this data storage. There are many benefits of cloud storage. Computer users do not need to purchase any hardware storage device to store their data. In addition, users can access their data via any device. Data and information stored in cloud storage are also used for disaster recovery. Moreover, cloud storage providers are responsible for the security of the user’s data. The cloud storage services are formed a great number of data centers to ensure data security. (Singh, 2020)
Most Used Storage Devices
There are many types of storage and types of storage devices and examples for each type are reviewed in this article. In addition, there are some advantages and disadvantages discussed previously. However, the computer industry is changing rapidly. Therefore, storage devices and their features can be obsolete rapidly and new storage devices can be introduced as replacements.
In nowadays, the most used storage devices are hard disks, USB flash drives, DVDs, and Blue-Rays. In addition, cloud storage has become used widely these days. Although the external hard disk is not a vital requirement for handling data in the computer, many computers use the external hard disk to increase their data storage capacity.
Characteristics of Computer Storage Devices
Characteristics of computer storage devices depend on the type and the mechanism behind this device. Therefore, the characteristics are different from device to device. All these storage devices are used to retain data or information. However, methods of storing data, specific and unique features, characteristics are reviewed under each storage device, throughout this article. Therefore, computer users will be able to compare these characteristics and choose the most appropriate storage device as their purpose and preference.
References
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