SECONDARY STORAGE DEVICES

Definition - What does Secondary Storage Device mean?

A secondary storage device refers to any volatile storage device that is internal or external to the computer. It can be any storage device beyond the primary storage that enables permanent data storage.

A secondary storage device is also known as an auxiliary storage device or external storage.

Secondary storage devices are primarily referred to a storage devices that serve as an addition to the computer's primary storage, RAM and cache memory. Typically, secondary storage allows for the storage of data ranging from a few megabytes to petabytes. These devices store virtually all programs and applications stored on a computer, including the operating system, device drivers, applications and general user data. Most of the secondary storage devices are internal to the computer such as the hard disk drive,

 the tape disk drive and even the compact disk drive and floppy disk drive.

Example of secondary storage devices:

Hard disk:

Hard disks are usually found inside computers to store programs and data. They are increasingly cheap and more and more companies are using them to back things up. Hard disks can vary in physical size with some disks getting as small as your thumb. The capacity of a commercial disk is currently up to about 4 terabytes allowing users to read and write to them. They are constructed from several key components:

Platter :

Metallic disks where One or both sides of the platter are magnetized, allowing data to be stored. The platter spins thousands of times a second around the spindle. There may be several platters, with data stored across them
Head - The head reads magnetic data from the platter. For a drive with several platters there may be two heads per platter allowing data to be read from top and bottom of each
Actuator Arm - used to move the read heads in and out of the disk, so that data can be read and written to particular locations and you can access data in a Random fashion, you don't need to read your way through the entire disk to fetch a particular bit of information, you can jump right there. Seek time is very low.
Power connector - provides electricity to spin the platters, move the read head and run the electronics
IDE connector - allows for data transfer from and to the platters
Jumper block - used to get the disk working in specific ways such as RAID
Hard drive-en.svg
For the exam you must be able to explain how a hard disk works:

The platters spin around the spindle

data is requested to be read from a particular area of a platter
the actuator arm moves the read head to that track
Once the data sector that is required has spun around and under the read head, data is read
Read data is sent from the IDE connector to main memory