1.2.2 Secondary storage

What are the features of secondary storage?

• slower because it is not directly accessed by the CPU (not directly embedded on the motherboard and can be external)

• typically larger in storage size

• non volatile- used for long term storage of files

• includes magnetic, optical and solid state storage

How does magnetic storage work?

• a read/write drive head moves nanometres above the disk platter and uses the magnetic field of the platter to read or write data to it

What are the features of magnetic storage?

• tracks - concentric circles, each of which are divided into sectors

• drive heads mounted on mechanical arms read and write data

• 500GB-12TB

What are the advantages and disadvantages of magnetic storage?

advantages

• large storage capacity

• cheaper cost per gigabyte - cheap to purchase

• faster access speed than optical storage

• reliable

disadvantages

• not durable due to moving parts that will eventually fail

• not portable when powered on - in a sealed unit for precision and moving can damage the device

• slower access speed than solid state

• noisy

• need to defragment

How does optical storage work?

• laser projects beam of light onto a spinning disk

What are the features of optical storage?

• data stored as pits and lands pressed into a spiral track circulating outwards from the centre

• laser passes over and measures the reflection, derviving 0s and 1s from this

• CD ROM up to 720MB

• DVD (dual layered) up to 8.4GB

• Blu Ray (dual layered) up to 50GB

What are the advantages and disadvantages of optical storage?

advantages

• cheap - especially in bulk

• portable - thin and lightweight

disadvantages

• low capacity compared to other storage types

• not durable - fragile, can break and scratch easily

• slowest access speed

How does solid state work?

• data is recorded onto solid chips without any moving parts

• large electric current is used to force electrons through a barrier and trap them on the other side

• they remain on the other side until flashed with a new current

What are the features of solid state?

• uses non volatile flash memory to store data

• does not have mechanoical movng parts

• 100TB -16TB

What are the advantages and disadvantages of solid state?

advantages

• large storage capacity

• usually durable and reliable - no moving parts

• portable - small physical size, compact, lightweight

• fastest access speed - no moving parts

• require little power

disadvantages

• more expensive cost per gigabyte

• cheap usb can snap or break

• limited write/rewrite cycles

What are the uses of magnetic storage?

• PCs

• storage of large amounts of data

• back up

• archiving

What are the uses of optical storage?

• multimedia storage

• back up

• archiving

What are the uses of solid state storage?

• higher end laptops

• smartphones

• tablets

• cameras etc