| · Explain the need for secondary storage within a computer system | Main memory is volatile and is lost without a power supply |
| Rank an SSD, HDD, and an optical disk for typical capacity
Include values | HDD: High, 500GB to 5000GB
SSD: Relativly low, under 1000GB
Optical disk: Very low, highest is about 25GB |
| Rank an SSD, HDD, and an optical disk for read write speeds
Include values
Include reasons why | SSD: Very high, around 500MB/s, has no moving parts
HDD: Good speed, about 100MB/s, has some moving parts
Optical disk: Relavitvly low, around 30MB/s, comprised of one main moving part |
| Rank an SSD, HDD, and an optical disk for power consumption | HDD: High
Optical disk: High
SSD: Low |
| How does an optical disk operate? | o Uses a laser, guided by a lens, to read and write
o A rotational mechanism will spin the disk
o To write power lens engravees disk with pits and labds correspinding to 1s and 0s
o Reading: Done by photodiodes detect the light reflected from the disk by a less powerful lens, this will be different due to the grooves reflecting light differently, and interpret this as 1s or 0s |
| In a HDD what is a block address | Address of a block |
| What is the commonest form of read write secondary storage | Magnetic disk drive
AKA HDD |
| Whats another name for a magnetic disk drive | HDD |
| What are the parts of a HDD ? | ??
o Platter rotation
o Read/write head
o Actuating arm
o Spindle
o Motor
o Platter
Correct:
Circular platter
Read/write head
Actuating arm |
| In a HDD what is track | One of the rings on a platter of a hard disk |
| In a HDD what is a sector | Subdivision of a track |
| In a HDD what is a block | Whole sector of track |
| Name ways in which HHDs can be kept the same size but their capacity increased | Adding more platters
Decreasing the width of tracks |
| State the principles of operation for HDDs | o Theres a number of circular platters which are made from magnetic material, above each is an arm which is a read/ write head
o Read/write head changes the polarity of parts of the platter
o The actuating arm allows the read/write head to access all portions of the platter
o Data is written into sectors |
| What is seek time | time to move the read/write head to the track |
| What is latency in the context of a HDD | time to rotate the actuating arm to the sector |
| How does an SSD work? | o SSD is formed of multiple blocks
o These blocks are formed of lots of pages
o These consist of memory cells which are formed of floating gate transistors which store information by trapping electrical charge
o The writing of information is dictated by the controller |
| Rank an SSD, HDD, and an optical disk for latency | HDD: High
SSD: very low
Optical disk: High |
| Rank an SSD, HDD, and an optical disk for portability
Include an explanation | HDD: Bad, bulky and heavy and easily damaged by movement
SSD: Good, lightweight and rarly damaged by movement
Optical disk: Okay, small and lightweight but can be damaged by scratches and dirt |
| Give some examples of what each secondary storage could be suitable for | HDD: Desktops, PCs, and servers
SSD: Laptops, tablets and phones
Optical disk: Sharing and distributing small volumes of data |
| Explain how information is recorded and read from a CD-ROM | s |
| Define an optical device | Use of a laser light to read from or write data to an optical disk |
| What are the parts of an optical device | o Laser
o Lens
o Photodiodes
o Rotational mechanism |
| Describe the pattern in which inforamtion is stored on an optical device and explain why it is done like this | In a spiral from the centre
So that users can directly access the files they’re interested in, without having to open any others. |
| Picture an SSD | ... |
| Labeled HDD | . |
| Picture an optical drive | . |
| Give the components of an SSD | NAND (flash) memory
Floating gate transistor
Controller |
| For an optical disk:
1. What are the engraved parts of a disk
2. What are the non engraved parts of the disk | Pits
Lands |
