Choosing suitable secondary storage

The choice of 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 ?
Capacity - how much 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
Cloud storage	Usually free for small amounts of space. Costs apply for more space	2 GB - 5 TB	Usually very fast (depending on internet speed)	Portable as files can be accessed from any device with an internet connection	Durable - nothing to break or lose as an individual but “cloud storage” companies could experience problems, such as server failure. However, data is usually backed-up	Usually reliable with an internet connection. But server failure or connectivity issues can happen, leaving users without access to their files until these issues are resolved	Used by individuals and many organisations globally, for sharing large amounts of data and collaborating on work
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	Cloud storage
Cost	Usually free for small amounts of space. Costs apply for more space
Capacity	2 GB - 5 TB
Speed of access	Usually very fast (depending on internet speed)
Portability	Portable as files can be accessed from any device with an internet connection
Durability	Durable - nothing to break or lose as an individual but “cloud storage” companies could experience problems, such as server failure. However, data is usually backed-up
Reliability	Usually reliable with an internet connection. But server failure or connectivity issues can happen, leaving users without access to their files until these issues are resolved
Typical use	Used by individuals and many organisations globally, for sharing large amounts of data and collaborating on work

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 or a CD-RW may be used to transfer files or to back up data.

Secondary storage and embedded systems - EduqasChoosing suitable secondary storage

Choosing suitable secondary storage

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