Computer Storage Devices

Computer storage device is a hardware that stores data either permanently or temporarily. These devices are used to store, porting or retrieving data files.

There are four types of storage in computers. Those are,

1.    Primary storage

2.    Secondary storage

3.    Tertiary storage

4.    Off-line storage

Primary storage

Primary storage act as short-term memory as known as main memory. These type of storage devices are store data temporarily. Random Access Memory (RAM), Read only memory (ROM) and Cache Memory are the examples of primary storage devices.

• RAM access data in a random order and much faster than other but RAM is a volatile memory. RAM stores data temporarily. There are two types of RAM.

1. DRAM (Dynamic RAM)

·      Slower than SRAM

·      DRAM needs to be refreshed thousands of time per second.

·      Less expensive and less power consumption

2. SRAM (Static RAM)

·      Faster than DRAM

·      SRAM not need to be refreshed

·      More expensive and more power consumption.

• ROM stores data on the computer permanently. This memory cannot be changed by program or user. ROM is non-volatile. There will be a small amount of ROM containing the boot firmware.
• Cache memory is a faster and smaller memory type. It used to reduce average time to access data from main memory. Older computer included only L1 cache but now most computers included L2 and L3 cache.

Secondary storage

Secondary storage is long-term storage which is not accessible by the CPU directly. These are non-volatile and slower than primary storage. Secondary storage refers to internal or external storage. There are mainly two types of storage devices. Those are Hard disk drives (HDD) and Solid state drives (SSD).

Hard disk is the largest data storage device in the computer which used to store portable data and backups. Hard disk drives can store from 160GB to 2TB. A hard disk unit comes with a set rotation speed from 4500-7200 rpm. Additionally, access time of a hard disk is measured in milliseconds.

 A hard disk drive uses read/write heads entering electro magnets to create magnetic charges on the medium. Following figure shows a part of computer hard disk.

Even though many computers hard drives as internal storage medium, hard drives can included as external as well such as Solid- state drives(SSD). Internal hard disks are less expensive than External disks.

Tertiary storage

Tertiary storage level is provide to extraordinarily large storage capacity without human operators at low cost. Therefore this is typically involves a robotic mechanism. For example magnetic tape and optical disk.

Offline storage (Disconnected storage)

Offline storage is portable and can be used on any computer system. This is the slowest and the cheapest option. Offline storage should be connected by a human operator before a computer can access it again. Common examples of offline storage include, Floppy disks, zip diskette, USB flash drive and memory card. Let’s consider them in order of increasing capacity.

Floppy disks

•Floppy disk is a portable and it is a soft magnetic disk.

•Even though it is a less expensive, it has less storage capacity (can store data up to 1.44MB).

Zip diskette

•Like a standard 1.44" floppy drive but more advance than that.

•capable to hold up to 100MB or 250MB but now it is less popular.

USB flash drive  

•USB flash drives are portable and small device and it plugs in to USB port as well as easy to transfer and store data.

•These are available in sizes from 2GB up to 256GB.

According to the above brief explanation can be got an idea about type of storage. Somehow there storage devices as well.

Let’s move to the type of storage devices.

There are four types that going to be explained in this.

1.    Magnetic storage devices

1. Optical storage devices

3.    Flash Memory devices

4.    Online Cloud storage devices

Magnetic storage devices

This is one of the most widely used type to store data as well as audio and video signal represent in binary form. Several types of magnetized media such as magnetic tape, floppy disks and hard drives.  

Magnetic tape:

·      Introduced by Fritz Pfleumer in 1928.

·      Tape is less expensive than other storage devices.

·      Commonly used for backups and also slower than other medium.

Floppy disk:

·      Introduced by IBM in 1969.

·      Also known as “Floppy diskette”

·      This is plastic cartridge measuring 3.5 inches square or 5.25 inches square and about 2mm thick.

·      Iron oxide was used to coat internally to store data in magnetic form.

Hard drives:

·      Introduced by IBM 1959 as secondary storage device.

·      According to the figure 1, a magnetic disks device contains iron particles.

·      A magnetic disk must be formatted before it can be used and during formatting, the drive creates circular tracks around the disk’s surface.

·      After dividing each track in to sectors, the operating system organizes it into groups named clusters.

                                                                                                                           (Banger, n.d.)

 Optical storage devices

All data saved as dot pattern and it can be easily read using laser beam. Optical storage can be reused and it has not only best durability but also ultra-data stability but it may getting trouble while recycling. 

Flash memory devices

Flash memory also known as EEPROM (Electronically erasable programmable read only memory). It has two transistors (floating gate and control gate) which are separated from each other by a thin oxide layer. Examples of flash memory devices:

• USB drives
• Memory cards
• Compact flash
• M.2 SSD and MMC(Multi Media Card)

Online cloud storage devices

Online cloud storage devices give agility, global scale and durability, with “anytime, anywhere” data access. There are many online cloud storage devices. For examples,

• Drop box
• Google drive
• iCloud
• Mega
• Microsoft one drive
• Box
• Google cloud platform
• Amazon drive

Drop box:

·      Operated by Dropbox, Inc., headquartered in San Francisco, California.

·      Offers cloud storage, personal cloud, client software and etc.

Google drive:

·  This allows to users to file storage in the cloud and file synchronization across devices and share files.

·   Microsoft windows is the platform and the official website is the “google.com”.

·   Google drive launched on 24th April, 2012.

iCloud:

·      This is an online cloud storage and the cloud computing service.

·      iCloud launched on 12th October, 2011.

What storage devices are mostly used??

The most common type of storage device is the hard drive. It is the main storage device in the computer. Primary hard drive stores the OS, folders and applications for users of the computer.

As well as external hard drives and USB drives are very common storage devices nowadays. These type of devices are often used for storing photos, videos and simply adding extra storage because these devices are portable.

Memory cards are used mostly to store digital information in mobile electronic devices.

At last let’s see characteristics of computer storage devices.

Characteristics of computer storage devices

Ø Volatility ( whether even after turn off the computer, the contents will be remain or not)

Ø Speed ( how quickly data can be accessed)

Ø Portability ( how easy it is to move it from a computer to another)

Ø Accessibility ( any location in storage can be accessed at any moment)

Ø Durability 

Considering the brief idea of this article, every computers or laptop or smartphone will have some kind of storage device with in it and if want to use external storage devices though those are available nowadays.

Mainly there are four types of storages such as primary storage, secondary storage, tertiary storage and offline storage. And also storage devices can be divided into four types so that Magnetic storage devices, optical storage devices, flash memory devices and online cloud storage devices. Finally some characteristics of computer storage devices have been mentioned.