1. Choosing the best storage method
Storage devices

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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