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1.3- Storage - Coggle Diagram
1.3- Storage
Optical Storage
- data stored using pits and lands
uses lasers to read and write data on optical disks- when light hits a pit, it's not reflected (0) and if it hits a land it's reflected (1) e.g. CDs, DVDs, Blu Ray Discs
capacity
- lower capacity than others (CD hold 800MB, DVD holds 4.7GB and Blu Ray disc holds up to 50GB)
speed
- slow to read and write as both must be done sequentially
portability
- ideal compared to larger secondary storage as it's smaller, lightweight and waterproof
reliability & durability
- not good as it can easily get scratched and become unreadable and it's hard to retrieve data then
cost
- cheap for small amounts of storage but expensive for large amounts compared to other types
Magnetic Storage
- data stored using magnetism
a read/write head moves over a magnetic surface to detect or modify magnetization e.g. hard disk drive, magnetic tapes (obselete)
capacity
- high capacity, up to terabytes
speed
- relatively fast but slower than flash memory
portability
- not ideal as it has moving/delicate parts so need to be treated carefully
reliability & durability
- can last a long time if protected and treated with care
cost
- very low per GB so ideal for backups
Solid State Storage
- data stored using semiconductor chips
contains multiple memory chips, controlled by software to make them act like a disk drive. They use flash memory e.g. solid state drive, memory stick
capacity
- large capacity, especially solid state drives
speed
- fast read/write speed but slower than hard disk drive if data is sequential
portability
- portable as memory sticks and SD cards are small and SSDs are kept in well protected casing and they all have no delicate/moving parts
reliability/durability
- reliable in short term but not long term as data will start to dissipate after a few years and if not plugged in for a while as data is stored by charge. Also has a limited number of read/write cycles
cost
- relatively expensive per GB compared to other secondary storage
Data Capacity
measure of how much data can be stored in a storage device
for memory calculations, remember to convert units into the same one (if different)
Need for Secondary Storage
A way is needed for data to be stored after power is turned off in a way that it can later be changed. RAM isn't suitable as data's lost after power is turned off and ROM isn't suitable as its data can't be changed
It is also needed for backups and archiving of data