2.1.2 Secondary storage

(s) explain the need for secondary storage
Secondary storage is needed to store programs/data and other files which would otherwise be lost when power is turned off.

(t) describe common storage technologies such as optical, magnetic and solid state

• Optical storage- CDs are a common example of optical storage which can usually store around 650Mb of data. A laser beam is used to burn data on to the surface of the disk and is also used to read data stored on a disk. CDs can either by ReWritable or CD-ROM, meaning the data can only be written once then cannot be changed.
• Magnetic storage- Magnetic storage devices such as magnetic tapes are used to store up to one terabyte of data, which is as much as can be stored on a hard disk. These are useful for storing and backing up large volumes of data.
• Solid state storage- Very flexible, can store many GBs of data. Inexpensive method of storage with no set up or driver software required.

(u)select suitable storage devices and storage media for a given application and justify their choice using characteristics such as capacity, speed, portability, durability and reliability.
Useful site- http://gcsecomputing.jimdo.com/unit-1-computer-systems-and-programming/secondary-storage/

Storage device:	Storage method	Typical capacity	Access speed	Usage
Floppy disk	Magnetic	1.44MB	36KBs	Transfering small files between machines
CD-ROM	Optical	650MB	6MBs	Distributing software / music
Magnetic Tape	Magnetic	50-160GB	12MBs	Backing up data on a server
DVD-ROM	Optical	4.7GB	33MBs	Distributing software, games and films
Hard disk	Magnetic	500GB	300MBs	Storing programs and data
Flash memory	Solid state	4GB-128GB	415MBs	Portable memory pens or replacement for hard disk