Choosing the best storage method Storage devices

Internal storage Internal storage is built into the computer Hard disk Stores: - Operating system - Application software - Data files ROM chip Stores BIOS data Loads operating system

External storage media External Storage is added to the computer as a peripheral Flash Memory Optical Storage CDs and DVDs Removable Hard Disk DAT Tape

Optical storage Digital Video Disks hold 4.7 Gb (single layer) or 8.5 Gb (dual layer) of data They are read by DVD drives DVD-ROMs are read only DVD-Rs can be written to once DVD-RWs can be written to and overwritten Compact Disks hold 650 Mb of data They are read by CD drives CD-ROMs are read only CD-Rs can be written to once CD-RWs can be written to and overwritten

External storage media Removable hard disks plug into the USB port They are available in very large capacities – many hundreds of Gb They can be used for extra storage or for back up They are quite large to carry around Flash memory cards can have a capacity of many Gb They are very small and suited to compact devices such as MP3 players and cameras They can be built into pen drives for data transfer They are not really suitable for back up

Server storage RAID disks give robust storage for servers They are available in very large capacities – many hundreds of Gb Drives can be mirrored for instant back up Drives can be hot swapped if one fails DAT tapes are often used to back up servers They have large capacity – up to 72Gb Data transfer speeds are quite low Tape is generally less reliable than disk storage They are small and easy to carry

Reasons for storing data Most common media Basic setup information – BIOS ROM To store files and programs for future use Hard disk, flash memory in compact devices To transfer it from one place to another CD-R, DVD-R, flash memory To back up important files in case of loss or damage Removable hard disk, CD-RW, DVD-RW, DAT tape

When choosing a storage method, consider: Remember When choosing a storage method, consider: Reason for storing data Volume of data Whether medium needs to be portable Speed of access needed Devices available Cost/benefit of buying new devices