3.3 data storage Flashcards
what is meant by primary storage
- directly accessed by CPU
examples of primary storage
- random access memory (RAM)
- read-only memory (ROM)
role of RAM
stores programs and data currently in use
features of RAM
- volatile (contents lost if RAM turned off)
- used to store data/files
- can be written/read
- content of memory can be changed
what is meant by secondary storage
- not directly accessed by CPU
- necessary for more permanent storage of data
role of ROM
stores start-up instructions and BIOS (basic input and output system)
features of ROM
- non volatile
- can only be read, cannot be written to (data stored cant be altered)
describe operation of magnetic storage
- uses platters (divided into tracks and sectors) on magnetic surface
- data read and written using electromagnets on read/write head
advantages of magnetic storage
- high capacity storage
- inexpensive
disadvantages of magnetic storage
- latency
- fragmentation
example of magnetic storage
hard disk drive (HDD)
describe operation of solid-state storage
- use NAND or NOR technology
- transistors used as control gates and floating gates
- store data by controlling mvmt of electrons within chip
advantages of solid-state storage
- durable (no moving parts)
- no latency (no moving parts)
- less power consumption and cooler
disadvantages of solid state storage
- higher cost per unit storage
- limited write cycles
examples of solid state storage devices
solid state drive (SSD), flash drives
describe operation of optical storage
- use lasers
- to create and read pits and lands
order optical storage devices by increasing storage capacity
why is this so
- compact disk (CD)
- digital versatile disk (DVD)
- blu-ray
smaller pit size and track width
describe CD
- red laser
- single layer
- slowest to access
describe DVD
- red laser
- dual layer
- faster to access
describe blu-ray
- blue laser
- single/dual layer
- fastest to access
describe what is meant by virtual memory
- memory management technique
- secondary memory can be used as if a part of primary
how is virtual memory created (w diagram)
- data and programs not currently in use transferred to virtual memory (in secondary) (page out)
- transferred back to RAM when needed (page in)
- programs stored as pages of data
why is virtual memory necessary
- memory management system
- RAM is full (run out)
- used so computer remains operational
what is meant by cloud storage
- data stored on remote servers
- accessed remotely
advantages of storing data on the cloud
- accessed at any time from any location with internet access
- no need to carry external storage device
- easy to extend storage
disadvantages of storing data on the cloud
- slow/unstable internet connection, cannot access data
- cost can be high if large capacity required
