Choosing suitable secondary storage
The choice of Non-volatile memory external to the CPU and used for long-term storage of programs and data. depends on the use it is required for. When deciding on the type of device needed, a user should consider:
- Cost - what is the cost per Gigabyte (GB) - a measurement of file size or storage capacity, 1,024 megabytes, or 1 billion bytes.?
- Capacity - how much Units of information. In computing there can be different data types, including integers, characters and Boolean. Data is often acted on by instructions. can the medium hold?
- Speed of access - how quickly can data be transferred to and from the medium?
- Portability - how portable is the medium? Does it need to be portable?
- Durability - how robust is the medium and how robust will it need to be?
- Reliability - how long-lasting is the medium?
Once these factors are taken into consideration an appropriate choice can be made.
| Medium and type | Cost | Capacity | Speed of access | Portability | Durability | Reliability | Typical use |
| Hard disk - magnetic | Cheap | 500 GB-12 TB | Slow | Internal devices are fixed. External hard disks are portable | Reasonable, but prone to damage if dropped or knocked | Generally very reliable if looked after | Long-term storage of programs and data |
| CD-ROM/R - optical | Very cheap | 640 MB | Very slow | Very portable | Easily scratched, damaged or broken | Generally very reliable if looked after | Backups, archives, copies of data or distribution of programs and music |
| CD-RW - optical | Very cheap | 640 MB | Very slow | Very portable | Easily scratched, damaged or broken | Generally very reliable if looked after | Copies of data or transferring files between computers |
| DVD-ROM/R - optical | Cheap | 4.7 GB | Slow | Very portable | Easily scratched, damaged or broken | Generally very reliable if looked after | Backups, copies of data, distribution of games, TV programmes and movies |
| DVD-RW - optical | Expensive | 4.7 GB | Slow | Very portable | Easily scratched, damaged or broken | Generally very reliable if looked after | Backups, archives or copies of data |
| Blu-ray-ROM/R - optical | Very cheap | 50 GB | Slow | Very portable | Easily scratched, damaged or broken | Generally very reliable if looked after | Distribution of TV shows and movies |
| Blu-ray-RW - optical | Very cheap | 50 GB | Slow | Very portable | Easily scratched, damaged or broken | Generally very reliable if looked after | Backups or archives |
| Solid-state drive - solid state | Very expensive | 256 GB-4 TB | Very fast | Internal devices are fixed. External hard disks are portable | Robust and resilient | Reliable | Long-term storage of programs and data where high performance is required |
| USB memory stick - flash memory | Expensive | 2 GB-2 TB | Fast | Very portable | Robust and resilient | Reliable | Copies of data or transferring files between computers |
| Medium and type | Hard disk - magnetic |
|---|---|
| Cost | Cheap |
| Capacity | 500 GB-12 TB |
| Speed of access | Slow |
| Portability | Internal devices are fixed. External hard disks are portable |
| Durability | Reasonable, but prone to damage if dropped or knocked |
| Reliability | Generally very reliable if looked after |
| Typical use | Long-term storage of programs and data |
| Medium and type | CD-ROM/R - optical |
|---|---|
| Cost | Very cheap |
| Capacity | 640 MB |
| Speed of access | Very slow |
| Portability | Very portable |
| Durability | Easily scratched, damaged or broken |
| Reliability | Generally very reliable if looked after |
| Typical use | Backups, archives, copies of data or distribution of programs and music |
| Medium and type | CD-RW - optical |
|---|---|
| Cost | Very cheap |
| Capacity | 640 MB |
| Speed of access | Very slow |
| Portability | Very portable |
| Durability | Easily scratched, damaged or broken |
| Reliability | Generally very reliable if looked after |
| Typical use | Copies of data or transferring files between computers |
| Medium and type | DVD-ROM/R - optical |
|---|---|
| Cost | Cheap |
| Capacity | 4.7 GB |
| Speed of access | Slow |
| Portability | Very portable |
| Durability | Easily scratched, damaged or broken |
| Reliability | Generally very reliable if looked after |
| Typical use | Backups, copies of data, distribution of games, TV programmes and movies |
| Medium and type | DVD-RW - optical |
|---|---|
| Cost | Expensive |
| Capacity | 4.7 GB |
| Speed of access | Slow |
| Portability | Very portable |
| Durability | Easily scratched, damaged or broken |
| Reliability | Generally very reliable if looked after |
| Typical use | Backups, archives or copies of data |
| Medium and type | Blu-ray-ROM/R - optical |
|---|---|
| Cost | Very cheap |
| Capacity | 50 GB |
| Speed of access | Slow |
| Portability | Very portable |
| Durability | Easily scratched, damaged or broken |
| Reliability | Generally very reliable if looked after |
| Typical use | Distribution of TV shows and movies |
| Medium and type | Blu-ray-RW - optical |
|---|---|
| Cost | Very cheap |
| Capacity | 50 GB |
| Speed of access | Slow |
| Portability | Very portable |
| Durability | Easily scratched, damaged or broken |
| Reliability | Generally very reliable if looked after |
| Typical use | Backups or archives |
| Medium and type | Solid-state drive - solid state |
|---|---|
| Cost | Very expensive |
| Capacity | 256 GB-4 TB |
| Speed of access | Very fast |
| Portability | Internal devices are fixed. External hard disks are portable |
| Durability | Robust and resilient |
| Reliability | Reliable |
| Typical use | Long-term storage of programs and data where high performance is required |
| Medium and type | USB memory stick - flash memory |
|---|---|
| Cost | Expensive |
| Capacity | 2 GB-2 TB |
| Speed of access | Fast |
| Portability | Very portable |
| Durability | Robust and resilient |
| Reliability | Reliable |
| Typical use | Copies of data or transferring files between computers |
In many situations, more than one type of secondary storage may be suitable. For example, a A physically small storage device. It normally plugs into a USB port. They are also called USB sticks, memory sticks, thumb or flash drives. These devices use solid state memory with no moving parts. or a CD-RW may be used to transfer files or to back up data.
Image caption, Hard disk drive
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