Computer storage devices

Definition

The computer needs a place to store data and program files when they are not in use. The purpose of storing is to hold data even when the computer is turned off. So storage device is used in the computers to store data Storage devices is used for storing, extracting data files and objects. Storage devices can store information temporarily and permanently. We can use storage devices internally or externally. We store data on storage devices in binary form. Many types of storage devices can be seen and each of them has benefits.

Usage of storage devices

The storage devices are mainly used for storing data. There are different types of storage devices and they have different types of advantages. They are different in size, shape. The Primary memory as RAM, ROM, and Cache is used for storing data in CPU. The secondary internal storage as Hard disk is used for saving frequently using digital data as well as the secondary external storage, offline storage, some flash memory storage online cloud storage is used for carrying data for transferring. The tertiary storage is served as a mass storage device. Tertiary storage such as Magnetic tape, Optical disc is typically used for data that is rarely accessed and this is useful for extremely large databases, accessed without human intervention.

Types of storage

There are four types of storage

• Primary storage
• Secondary storage
• Tertiary storage
• Offline storage

Primary storage

Primary storage is also called main memory. Main memory is directly or indirectly connected to the central processing unit via the memory bus. The CPU constantly reads instructions stored on it and executes them as needed. In primary storage, we can read and write data quickly. We can identify different types of primary storage.

• RAM — RAM is called Random access memory. Because any of the data in random access memory can be accessed just as fast as any of other data. RAM stores data till the computer is working. When the computer is turn switched off, data is erased. RAM is volatile because when there is a power failure data stored data is lost.

There are two types of RAM

• DRAM ( Dynamic Random Access Memory)
• SRAM (Static Random Access Memory)

o Dynamic Random Access Memory

DRAM is continually refreshed to maintain the data. The refreshing is performed by memory placed on a refresh circuit, it rewrites the data several hundred times per second. DRAM is cheap and small. All DRAMs are made up of memory cells consisting of one capacitor and one transistor

o Static Random Access Memory

SRAM does not need to be refreshed regularly. SRAM chips use a matrix of six transistors and no capacitors. SRAM uses more chips than DRAM for the same account of storage space. The cost of manufacturing SRAM is higher.

• ROM — ROM means Read-Only Memory. ROM is used as the computer begins to boot up. Small programs like firmware are often stored in ROM chips on hardware devices. ROM memory cannot be easily or quickly overwritten or modified. So ROM is non — volatile. ROM is hold data when power is turned off.
• Cache — Cache memory is small in size and volatile memory. It provides high-speed data access to a processor and Cache stores frequently used computer programs, applications and data. Cache makes data retrieval easy and efficient. The cache acts as butter between RAM and the CPU. Most computers today come with L3 cache and L2 cache, and older computers included an only L1 cache.

Secondary storage

Secondary storage is non-volatile, low cost, high capacity, portable or not. This is long-term storage. If there is secondary storage in the computer we can store data permanently. Secondary storage is also known as additional memory or auxiliary memory. Secondary storage could be internal or external. Hard disk drive, the tape disk drive, CD- ROM, BLU — ray, DVD, and floppy disk drive are used as internal storage. USB flash drives, and plug and play devices are used as external storage.

Example for secondary storage devices

• Solid-state drives
• Hard disk drives
• Cloud storage
• CD — ROM
• DVD drives
• Blu-ray drives
• USB Flash drives
• SD cards
• Floppy diskette
• Tape drives
• Zip and Jaz drives

The hard disk drive as an example

The hard disk drive is the primary and usually largest data storage device on your computer. It can store data from 160 gigabytes to 2 terabytes. A hard disk speed is a speed at which content can be read and written on a hard drive. The set rotation speed of the hard drive is from 4500 to 7200rpm. Disk access time is measured in milliseconds. There are two types of hard disks,

• Internal hard disk
• External hard disk

Internal hard disk is not portable, less expensive, fast, and big but external hard disk is portable, more expensive, slow, and small in size.

Tertiary storage

The removable storage devices are used as tertiary storage devices. Tertiary storage provides the third tier of storage. They are primarily useful for large data stores, accessed without human intervention. Tertiary storage includes a robotic mechanism that will mount and dismount removable mass storage media into a storage device as required by the system. When a computer needs to read information from the tertiary storage, it first consults a catalog database to determine which tape or disc contains the information. The computer will then use a robotic arm to fetch the medium and place it in a drive. When the computer finishes reading the instruct information. The robotic arm will return the medium to its place in the library. Tertiary storages are inexpensive and removable.

Examples -

• magnetic tape

A magnetically coated strip of plastic on which data can be encoded. Tapes for computers are similar to tapes used to store music. Tape is inexpensive than other storage mediums. That is commonly used for backup.

• Optical disc

An optical disc is any storage media that is digitally contained in digital format and readable by laser assembly which is considered an optical media. The most common types of optical media are,

• Blu-ray disc
• Compact disc
• Digital versatile disc

Offline storage

Off-line storage is also known as disconnected storage. Off-line is a computer data storage on a medium or a device that is not under the control of a processing unit. Before re-accessing a computer, it must be entered or connected by a human operator. The stored data are remaining permanently in an offline storage device even if the computer is disconnected from it. Offline storage devices are portable and can be used in different computer systems. This is often used for transferring data

Example -

• floppy disk

A Floppy disk is a soft magnetic disk. These are portable. Floppy disks are slower than hard disks and floppy disks have less storage capacity. But floppy disks are inexpensive.

• Zip diskette

Zip diskette is a hardware data storage device. It was developed by Iomega. It performs like a standard 1.44’’ floppy drive. They can hold up to 100MB of data or 250MB of data on mew drives. Now these are less popular because of their small storage capacity.

• USB Flash drive

They are small and portable memory cards that act like portable hard drives.it can be connected to the computer by the computer’s USB port. There are different sizes of flash drives such as 2GB, 4GB, and up to 256GB.

• Memory card

A memory card is an electronic flash memory storage disk. It is commonly used in consumer electronic devices such as digital camera’s MP3 players, mobile phones, and other small portable devices. Memory cards are usually read by connecting the devices containing the card to your computer or by using a USB card reader.

Types of computer storage devices

There are four types of storage devices

• Magnetic storage devices
• Optical storage devices
• Flash memory devices
• Online cloud storage devices

Magnetic storage devices

All data are stored using a magnetized medium and data saved in the binary form of 0s and 1s. Magnetic storage is non-volatile storage. Read and write data in magnetic storage devices is very easy so most people like to use magnetic storage devices. Magnetic storage devices have a large capacity for data storage. But the accessing the data is slow. These devices are cheap.

Examples-

• hard drive
• Floppy disk
• Magnetic tape

Optical storage devices

The information is stored at an optical disk in the optical storage devices. This is most useful for huge data storage. Optical storage devices are cheap, lightweight, and easy to transport. As well as these are removable devices. Optical storage devices can be recycled or re-used. One of the disadvantages of optical storage is some traditional PCs are not able to read these disks. An optical device writes data by shining a laser onto the disc. This can only be written once but read many times.

Examples-

• CD-ROM
• DVD-ROM
• Blur Ray
• HD DVD
• DVD RAM
• CD-R & DVD R

Flash memory devices

Flash memory was invented by Dr.Fujio Masuoka at Toshiba in 1980. It is based on EEPROM (Electronically Erasable Programmable Read-Only Memory) Technology. Flash memory devices are non-volatile and we can write and erased programming electrically. Flash memory devices are used for storing data to computers as well as electronic devices such as USB flash drives, MP3 players, and Digital cameras, and solid-state drives. There are two types of flash memory based on using technology

• NOR flash memory
• NAND Flash memory

Flash memory devices are a higher speed of reading and write .these are small in size, portable, consuming less power, low chance to damage, not much cost.

Examples-

• USB flash drive
• Memory card
• Compact Flash
• MMC
• SDHC Card
• SD card

Online cloud devices

Cloud storage is a form of cloud computing model that stores data on the internet through a cloud computing provider. These cloud storage providers are responsible for ensuring the data is available and accessible as well as the physical environment secured, protected, and running. People and organizations purchase or lease storage capacity from the providers to store user, origination, or application data. There are three types of cloud storage depending on storage used.

They are,

• Object storage
• File storage
• Block storage

Furthermore, there are three main cloud storage options based on different access.

• Public cloud
• Private cloud
• Hybrid cloud

Examples -

• Dropbox
• iCloud
• Google Drive
• Microsoft one drive
• Box
• Mega

Most used storage devices

Today, most people use a different types of storage devices. Among them the most used storage devices are,

• USB flash drives
• Hard disks
• Optical disk

The USB drive become the most used storage device today because USB drives are small, lightweight, and can be taken anywhere. It can store documents, images, music files, and videos. so USB drive become most popular as well as most used storage device

The hard disk is also the most used storage device now a day. Hard disk is used for storing all types of small or big files or data of computer. The hard disk can store data speed. It has a long life span. There are two types of the hard disk. They are internal and external. Internal hard disks are used in computers. These are not portable, big but external hard disks are portable, small in size comparing internal hard disks, external hard disks are more expensive and slow. However hard disks are one of the most used storage devices.

Optical disks are used today but not like in the past. Still, it has demand. Because these are inexpensive, ability to write data quickly, long media life, mass storage capacity.

Characteristics of computer storage devices

Volatility — among computer storage devices some are volatile and others are non — volatile. In volatile storage devices, when the computer is turned off, stored data will be lost. As an example-RAM. In non-volatile storage devices even if power is turned off, data will store. Most secondary, tertiary, and off-line storage is non-volatile.

Speed — speed measures that how much time takes a device to read or write data. Most internal storage devices are speed than external storage devices as an example internal hard drive is speed than an external hard drive.

Portability — most storage devices can carry anywhere for example -USB, Optical disks. These are small in size as well removable but some storage devices are located in the computer or any other devices. These are normally big and not removable. Internal storage devices are difficult to carry anywhere.

Cost — capacity, portability, the durability of storage devices are affected by cost. Storage devices which can store a large capacity of data are expensive.

Durability — if something is durable. It can be able to withstand give up physical movements. Especially portable storage devices should be durable. These are carried anywhere. So portable storage devices should be durable to prevent easy damage.

References

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