Suitable devices and storage media for a given application
The choice of secondary storage medium 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)?
- Capacity - how much data 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 resilient and long-lasting is the medium?
Once these factors are taken into consideration, an appropriate choice can be made.
Storage media comparison table
| Medium | Type | Capacity | Speed of access | Portability | Durability | Reliability | Typical use |
| Hard disk | Magnetic | 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 | 640 MB | Very slow | Very portable | Easily scratched, damaged or broken | Generally very reliable if looked after | Backups, archives, copies of data, distribution of programs and music |
| CD-RW | Optical | 640 MB | Very slow | Very portable | Easily scratched, damaged or broken | Generally very reliable if looked after | Copies of data, transferring files between computers |
| DVD-ROM/R | Optical | 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 | 4.7 GB | Slow | Very portable | Easily scratched, damaged or broken | Generally very reliable if looked after | Backups, archives, copies of data |
| Blu-ray-ROM/R | Optical | 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 | 50 GB | Slow | Very portable | Easily scratched, damaged or broken | Generally very reliable if looked after | Backups, archives |
| Solid-state drive | Flash memory | 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 | 2 GB-2 TB | Fast | Very portable | Robust and resilient | Reliable | Copies of data, transferring files between computers |
| Medium | Hard disk |
|---|---|
| Type | Magnetic |
| 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 | CD-ROM/R |
|---|---|
| Type | Optical |
| 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, distribution of programs and music |
| Medium | CD-RW |
|---|---|
| Type | Optical |
| 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, transferring files between computers |
| Medium | DVD-ROM/R |
|---|---|
| Type | Optical |
| 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 | DVD-RW |
|---|---|
| Type | Optical |
| 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, copies of data |
| Medium | Blu-ray-ROM/R |
|---|---|
| Type | Optical |
| 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 | Blu-ray-RW |
|---|---|
| Type | Optical |
| 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, archives |
| Medium | Solid-state drive |
|---|---|
| Type | Flash memory |
| 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 | USB memory stick |
|---|---|
| Type | Flash memory |
| Capacity | 2 GB-2 TB |
| Speed of access | Fast |
| Portability | Very portable |
| Durability | Robust and resilient |
| Reliability | Reliable |
| Typical use | Copies of data, transferring files between computers |
In many situations, more than one type of Non-volatile memory external to the CPU and used for long-term storage of programs and data. may be suitable. For example, a USB stick or a CD-RW may be used to transfer files, or to back up data.
Image caption, Hard disk
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