Optical Magnetic and Solid State Storage

Storage Devices

A data storage device is a device for recording (storing) information (data). Recording can be done using virtually any form of energy, spanning from manual muscle power in handwriting, to acoustic vibrations in phonographic recording, to electromagnetic energy modulating magnetic tape and optical discs.

A storage device may hold information, process information, or both. A device that only holds information is a recording medium. Devices that process information (data storage equipment) may either access a separate portable (removable) recording medium or a permanent component to store and retrieve information.

Electronic data storage requires electrical power to store and retrieve that data. Most storage devices that do not require vision and a brain to read data fall into this category. Electromagnetic data may be stored in either an analog data or digital data format on a variety of media. This type of data is considered to be electronically encoded data, whether or not it is electronically stored in a semiconductor device, for it is certain that a semiconductor device was used to record it on its medium. Most electronically processed data storage media (including some forms of computer data storage) are considered permanent (non-volatile) storage, that is, the data will remain stored when power is removed from the device. In contrast, most electronically stored information within most types of semiconductor (computer chips)microcircuits are volatile memory, for it vanishes if power is removed.

Optical Storage

Optical storage devices save data as patterns of dots that can be read using light. A laser beam is the usual light source.

The data on the storage medium is read by bouncing the laser beam off the surface of the medium. If the beam hits a dot it is reflected back differently to how it would be if there were no dot. This difference can be detected, so the data can be read.

Dots can be created using the laser beam (for media that is writable such as CD-Rs). The beam is used in a high-power mode to actually mark the surface of the medium, making a dot. This process is known as ‘burning’ data onto a disc.

Magnetic Storage

Magnetic storage media and devices store data in the form of tiny magnetized dots. These dots are created, read and erased using magnetic fields created by very tiny electromagnets.

In the case of magnetic tape the dots are arranged along the length of along plastic strip which has been coated with a magnetizable layer (audio and video tapes use a similar technology).

In the case of magnetic discs (e.g. floppy disc or hard-drive), the dots are arranged in circles on the surface of a plastic, metal or glass disc that has a magnetizable coating.

Magnetic Tape

Magnetic tape is a large capacity, serial access medium. Because it is a serial access medium, accessing individual files on a tape is slow.

Tapes are used where large amounts of data need to be stored, but where quick access to individual files is not required. A typical use is fordata back-up (lots of data, but rarely only accessed in an emergency)

Tapes are also used and in some batch-processing applications (e.g. to hold the list of data that will be processed).

Solid State Storage

Hard Drives

Hard-drives have a very large storage capacity (up to 1TB). They can be used to store vast amounts of data. Hard-drives are random access devices and can be used to store all types of films, including huge files such as movies. Data access speeds are very fast. Data is stored inside a hard-drive on rotating metal or glass discs (called ‘platters’).

Fixed Hard Drive

A hard-drive built into the case of a computer is known as ‘fixed’. Almost every computer has a fixed hard-drive. Fixed hard-drives act as the main backing storage device for almost all computers since they provide almost instant access to files (random access and high access speeds).

Portable Hard Drive

A portable hard-drive is one that is placed into a small case along with some electronics that allow the hard-drive to be accessed using a USB or similar connection.

Portable hard-drives allow very large amounts of data to be transported from computer to computer.

Many portable music players (such as the iPod classic) contain tiny hard-drives. These miniature devices are just not much bigger than a stamp, but can still store over 100MB of data!


A Solid State Drive (SSD) is a type of computer storage drive which makes use of flash memory chips such as is found in smartphones, memory cards and USB drives. (1) (2)

In contrast, a mechanical Hard Disk Drive (HDD) possesses a platter on which data is stored, a motor which spins the platter (to speeds up to 7200 revolutions per minute), and an actuator arm which physically moves "read" and "write" heads which seek for and add data to the spinning platter. All these moving parts are the reasons why solid state drives perform better than hard disk drives. However, SSDs in spite of their advantages over HDDs still have notable disadvantages.

The pros and cons of solid states drives are discussed below:


  • More Durable: Subjecting a mechanical hard disk drive to shock such as by dropping it can cause considerable damage. For example, the actuator arm may break off or scratch the platter (leading to the loss of data located in the scratched area). An SSD can withstand such handling better than HDD because it lacks all the above mentioned moving parts. The lack of these parts in SSDs also means that less wear and tear occurs.

  • Better Computer Performance: Solid state drives improve the performance of a computer in the following ways:

  • Faster Read and Write Speed: On a solid state drive you do not have to wait for the drive platter to be spun up by the hard drive's motor as occurs in a mechanical hard drive. You also do not have to wait for the actuator arm to move the read/write heads which physically seek for or add data to the drive. Reading and writing data to the flash memory chips which make up SSDs occurs instantly. This allows SSDs to have greatly faster read and write speeds than HDDs.

  • File Fragmentation Has Little Impact: File fragmentation occurs on storage drives because data is not always stored at its original location especially when it constantly edited, changed or deleted. This reduces the performance of mechanical hard disks because the "read" head has to physically look for the required data in all the locations where it may be stored. File fragmentation is a non-issue in solid state drives because of the constant read performance of such drives. Data is instantaneously accessed no matter where it is stored.



  • Expensive: The main disadvantage of solid state drives is that they cost a lot more for the same amount of storage capacity as hard disk drives.

  • Limited Storage Capacity: SSDs are very expensive to produce and sell at exorbitant prices when compared to HDDs. Thus, they are usually available in smaller, more affordable storage sizes such as under 160GB.

  • Slower Write Speed on Some Models: Less expensive SSDs (MLC based types) typically have slower write speeds than read speeds. These speeds can be slower than the write speeds on HDDs.

  • Relatively Newer Technology: The increasing use of solid state drives is a recent development and so many issues need to be resolved before optimum performance can be obtained from using them. For instance, Windows operating systems before Windows 7 were not optimized to use SSDs. Using an SSD with an un-optimized OS such as Windows Vista will reduce performance and shorten the life span of the drive.

  • Unreliable Life Expectancy: Some types of solid state drives specifically those that make use of NAND flash memory chips have a limited number of times that they can be written to. SSDs that make use of DRAM technology do not have such a limitation but they are much more expensive.

  • Inability to Recover Lost Data: One of the advantages of SSDs is that they allow you to permanently and absolutely delete data from such drives. However, such permanent deletion may have irreparable consequences in situations where no backup has been created for the deleted data.