1.3 Storage Flashcards
What are the three tiers of storage?
Primary
Secondary
Tertiary
Define primary storage.
Give four examples
Memory areas that the CPU access is directly and quickly. Has the fastest read/write speeds and is mostly volatile
This includes registers, cash, ROM and RAM
Define secondary storage
Nonvolatile, read/write, permanent memory which is not directly accessed by the CPU, and his data must be transferred into main memory before being processed by the CPU
Define tertiary storage
External, non-volatile, high capacity memory used for archives and backups by large companies
Give a typical example of tertiary storage
A magnetic tape library which may use a robotic arm to access the tapes
Why is secondary storage required?
A way of storing data and files permanently and long-term – must be non-volatile and read/writeable
How is data stored on optical discs?
As microscopic indentations (pits and lands representing 0s and 1s) on a disc’s reflective surface in a spiral track running from inside to outside of disc
What is the capacity of a CD? DVD? BD?
CD = 700 MB DVD = 4.7 GB BD = 25 GB +
Why are optical discs falling out of use?
Streaming and downloading as internet speeds have increased remove the need for optical discs
Modern devices such as smartphones don’t have optical drives
Can’t compete with flash memory for backups – low capacity, slow read/write speed and poor reliability of read/write discs
How is data stored in magnetic storage?
As opposite magnetic polarities in sectors within tracks on a magnetise metal platter, which makes up one of many stacked on top of each other, spinning at 5400 - 15000 rpm
What is the traditional internal storage for a computer?
HDDs
What is a read/write head made of?
Electromagnets
What are the advantages of SDDs over HDDs?
Faster Don’t need defragmenting No noise No heat More shock-proof
What is flash memory?
Data is stored in arrays of transistors, which are either on or off, representing zeros and ones
Faster boot up times and faster opening of programs and files is given by …
Solid state storage
What is the physical appearance of magnetic tape? What does it require?
Comes in plastic cassettes which require a special tape-drive to read/write
How is data written into magnetic tape?
Sequentially
What happens if an HDD is hit?
The data is corrupted when the head hits the platters
Reliability of optical discs
Stored data degrade over time
Data access time of HDDs
Milliseconds
Data access time of SDDs
Nanoseconds
How is data accessed on an HDD?
Random Access
Cost of optical discs
Very low
Why is the cost of solid state so high?
Relatively young technology
