Presentation By Saurabh Mishra A data storage device is a device for recording storing information data CD Hard Disk and Flash media are the main s torage devices used today STORAGE DEVICES ID: 147306
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Slide1
STORAGE DEVICES
Presentation By:
Saurabh MishraSlide2
A
data storage device
is a device for recording (storing) information (data). CD, Hard Disk and Flash media are the main storage devices used today.
STORAGE DEVICESSlide3
COMPACT DISC
Compact Disc (CD) is a circular disc of diameter of 120 millimetres (4.7
in)A CD can hold up to 80 minutes of uncompressed audio or 703 MB.
The below diagram shows the construction of a CD.Slide4
Understanding the CD
A CD has a single spiral track of
data circling from the inside of the disc to the outside.
Spiral
track starts at the
centre means that the CD can be smaller than 4.8 inches (12 cm) if
desired.
Mini CD of diameter only 2.
4 inches ( 6cm) used for delivering device drivers.Slide5
Understanding the CD: Bumps
A laser of wavelength 780 nm is used to ‘burn’ pits (bumps) on CD track.
The
elongated bumps that make up the track are each 0.5 microns wide, a minimum of 0.83 microns long and 125
nm high.
If you could lift the data track off a CD and stretch it out into a straight line, it would be 0.5 microns wide and almost 3.5 miles (5 km) long!Slide6
CD Player
A
laser and a lens system focus in on and read the bumps.
The CD layer reflects the laser, at pits reflected value is a 0
and else it is 1.
A tracking mechanism moves the laser assembly so that the laser's beam can follow the spiral track.
A drive motor spins the disc at a speed between 200 to 500 rpm.Slide7
Digital Versatile Disc
A DVD has almost 6 times (up to 4.7 GB) data storage capacity then a CD.
The more storage capacity of a DVD is duo to less separation between tracks and less size of track.Slide8
Flash Drives
Flash memory refers to a type of computer technology that stores data, does not need constant electricity, and can be electrically erased and reprogrammed.
Flash
memory is used in many different appliances including memory cards,
PDAs.
Information is stored in an array of memory cells made from floating-gate (FG)
transistorsSlide9
Flash Memory CellSlide10
The
top gate is called the control gate while the bottom is called the floating gate.
The floating gate is completely insulated with an oxide layer. Each memory cell of a USB flash drive is a floating-gate transistor.
When an electron is attached to the floating gate, it is trapped within the oxide layer and causes a difference in the voltage of the control gate.
When
this is measured as a whole, each memory cell makes up a 1 or 0 in binary code, depending on whether it is storing an electron or not.
Working of Flash DrivesSlide11
NOR Flash
Memory
Developed to replace read only memoryFull address and data buses allow random access to any memory
location
Can
access any memory
cell
Slow
sequential accessNAND
Flash
Memory
Developed to replace hard
disks
Sequential-accessed command and data registers replace the external bus of
NOR
Decreases chip real
estate
Can
only access
pages
Faster sequential
accessSlide12
Hard Disks
A hard disk drive (
HDD)
is
a data storage device used for storing and retrieving digital information using rapidly rotating disks (platters) coated with magnetic material
.
An HDD retains its data even when powered off
.
Data rate - The data rate is the number of bytes per second that the drive can deliver to the CPU. Rates between 5 and 40 megabytes per second are common
.Slide13
Understanding the Hard Disk
The platters
- These typically spin at 3,600 or 7,200 rpm when the drive is operating. In order to increase the amount of information the drive can store, most hard disks have multiple
platters.
The
arm
- This holds the read/write heads and is controlled by the mechanism in the upper-left corner. The arm is able to move the heads from the hub to the edge of the drive.Slide14
Data is stored on the surface of a platter in sectors and tracks.
Tracks
are concentric circles, and sectors are pie-shaped wedges on a
track.
A sector contains a fixed number of bytes -- for example, 256 or
512.
The process of low-level formatting a drive establishes the tracks and sectors on the platter
.
The process of low-level formatting a drive establishes the tracks and sectors on the platter.Slide15
An HDD records data by magnetizing a thin film of ferromagnetic
material
on a disk.Sequential changes in the direction of magnetization represent binary data bits.
The
data is read from the disk by detecting the transitions in magnetization.Slide16
References
computer.howstuffworks.com
w
ikipedia.com
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