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Secondary storage is also known as auxiliary storage or external storage. These devices store the data after it has been stored in the primary storage devices Ruane, 2013. Secondary storage devices include all the data or information that is not in the primary memory of the computer.
Management of Data in Secondary Storage Devices
Data storage, also known as memory, is of two kinds. One is primary storage and other is secondary storage of data. Storage of data is basically a technology in which instructions for execution and digital data is recorded and saved with the help of certain computer components. It is a very essential and core part of a computer (Kissoon, 2011). Management of data in secondary storage devices is very easy and can be accesses whenever needed. Secondary storage devices are of three types, magnetic devices, optical devices and solid state storage devices.
Figure : Secondary storage devices
Whenever, we use a computer to make any document that contains the information we want to write, then it is saved in primary storage devices, i.e. RAM. Random Access Memory stores that information for certain time and all the data is deleted when computer is turned off. So, secondary storage devices play their role in store data in such a way that it is stored permanently. These devices are slower comparative to primary devices, because they are not directly accessible by the CPU (Ruane, 2013).
Mechanism of Reading and Writing data on various devices
The magnetic devices are such type of secondary storage devices that record and store information on a magnetized medium. This type of storage device uses a magnetic head to read and write the data (Wikipedia). They use different patterns to store the information and they are a type of non-volatile memory. The magnetized medium used can be a plastic tape coated with a metal. The examples of such types of magnetic devices include audio recording and tape storage devices.images.jpg
Figure : Magnetic Tape
The magnetic storage devices work on the principal of magnetic charge. The basic principle is that a magnetized medium can be magnetized by an electric magnet. As the information is moved on the magnetic head devices called read-and-write head, it can easily be written and read from the storage medium. The magnetic head is used for the detection and modification of the material. The information is recorded in the form of binary digits, which are 0 or 1. After this process, it can then be read magnetically and its recorded data played back (Elliott, 2004).
Magnetic storage devices primarily include hard disks, floppy disks, magnetic recording tapes and magnetic disks. The main difference in operation of reading and writing between tapes and disks is that all the information or data can be written or read from any location on a disk. Tapes are sequential devices as they have a beginning and an end of information. If we want to have the information and read it from middle, then we cannot access it and we will have to fast-forward everything from beginning. All the data is properly organized into sectors in a disc.
Figure : Hard-drive
Figure : Floppy Disc
The optical storage devices use the laser light or electromagnetic waves in order to read write and store data on the optical disks. The most common types of optical devices include compact discs or CDs, DVDs and Blue-ray disks. The most widely used optical device is the CD-ROM, for compact disk read-only memory.
Figure : CD-ROM
Its working principle is different from magnetic devices. The technology of these devices is that the laser light hits the layer of metallic material spread over the surface of a disk. When any information is transferred on the disc, the tiny spots are produced on the surface of disc. These spots are due to the heat coming from the laser. Optical storage devices are distinguished as they have the read or write capability. The CDs are not used for storing files, but are used for storing large memory software. Many people use these devices to store the movies and songs, which can be played from anywhere unlike magnetic discs. All the application software can easily be stored in these devices as there is a room full of memory and capacity. The manufacturer can record read-only media and the user can only read the information but cannot write it (Sklavos, 2008).whatsnew-compressor-discs-20090722.jpg
Figure : Blu-ray Discs
Solid State Storage devices
This type of computer storage devices are made up of microchips of silicon. Solid state storage devices store all the information electronically, instead of magnetically. There are three types of such devices, which are solid-state drives, solid state cards and solid state modules. It is also non-volatile memory storage and the data remains even if the computer is shut down. The examples of these devices are adapter cards, SD cards, SIM cards and flash or USB drives (Baker, 2013).
There working technology is that they are flashed-based systems that have finite number of writes. The mechanism for reading and writing of solid state storage devices is comprised of erasable blocks each comprising a plurality of data write locations.solid_state_storage_01.jpg
Figure : Solid-state Storage Devices
Efficient Storage device
The most efficient storage device among secondary storage devices is SSD. Magnetic hard discs are better than DVDs or optical devices. The reason is that they offer the fastest seek time and transmission rate of 5-10 MB/second. But Solid state storage devices are better than hard-discs as they allow the transfer of data with highest speed and provide more lifespan for storage. It also offers the same levels of data integrity and endurance as other electronic devices and requires less power and cooling than its electromechanical equivalents. It also generally weighs less (Baker, 2013).