This document discusses different types of secondary storage devices, including magnetic tape, magnetic disks, optical disks, and magneto-optical storage devices. It provides details on the structure, organization, and read/write process of various magnetic storage media like magnetic tapes, floppy disks, hard disks, and zip disks. Magnetic tapes provide inexpensive storage but are sequential access devices. Magnetic disks like hard disks enable direct access and are widely used as primary storage.
2. contents
Types of Secondary Storage Devices
Magnetic Tape
Magnetic Disk
Types of Magnetic Disks
Optical Disk
Types of Optical Disks
Magneto-Optical Storage Devices
Universal Serial Bus
Memory Stick
Mass Storage Devices
3. Types of secondary storage
devices
Secondary storage facilitates storing the data and
instructions permanently.
There are to methods of accessing data from
secondary storage devices
Sequential access
Direct access
5. Sequential access
Means the computer system must search the
storage device from the beginning until the
desired data is found.
Eg: magnetic tape where data is stored and
processed sequentially.
Suppose there is information regarding
employees of organization, to look into
information of employee number 100, the
computer will have to start with employee number
1 and then go to 2,3 and so on till 100.
This method is simple , but searching a data
takes a lot of time.
6. Direct access
Also known as random access.
Computer can go directly to the location where
the data that the user wants , are stored.
Eg: magnetic disk, optical disk
Data is stored as sequentially numbered blocks.
One can access clock 12, the 72 then 2 so on, in
any fashion.
Used in systems that is used for airline
reservation, computer based assistance systems
No fixed patterns of request for data
8. Magnetic tape
Appears as same that of music cassettes.
It is plastic tape with magnetic coating on it.
Data is stored in the form of tiny segments of
magnetized and demagnetized portions on the
surface of the material.
The magnetized portion of the tape refers to the
bit value ”1” and demagnetized portion refers “0”
9. They are available in various sizes
Major difference is speed at which the tape is
moved past the read/write head and the tape’s
record density.
The amount of data is the number of binary digits
that can be stored on a linear inch of the tape is
the recording density of the tape.
They are very durable, can be erased , reusable
Inexpensive, reliable storage for organizing
archives medium , taking backups
10. Not suitable for the data files that need to be
revised or updated often , because data is stored
in sequential manner, rewinding and advancing
the tape is required for updating the data.
If the tapes stretches too much, the it will render
itself unusable for data storage and may result in
data loss.
Today primary role of tape drive is for backing up
or duplicating the data stored on the hard disk to
protect the system against loss of data during
power failures or computer malfunctions.
13. Magnetic tape organization
Divided into vertical columns (frames) and
horizontal rows (channels or tracks)
Data stored in a string of frames with one
character per frame, each frame spans multiple
tracks.
A single bit is stored in each track, one byte per
frame.
The remaining track will store the parity bit.
When a byte is written to the tape, the number of
1s in byte is counted, the parity bit is then used to
make the number of 1s even or odd.
14. When the tape is read again, the parity bit is
checked to see if any bit is lost
Magnetic tape drives two reels:
Supply reel and take-up reel
both are mounted on the hubs and the tape
moves from the supply reel to take-up reel
The magnetic oxide coated side of the tape of
passes directly over the read/write head
assembly, thus making contact with the heads.
15. As the tape passes directly
under the read/write head,
the data can be either read
and transferred to the
primary memory or read
from the primary memory
and written on to the tape.
18. Information format of magnetic tape
Physical marking to indicate the location from
where reading and writing on the tape is to begin
BOT- beginning of the tape
EOT- End of the tape
Usable recording surface length between BOT
and EOT
BOT/EOT are usually made up of reflective type
of short silver strips.
These are sensed by the arrangements of lamps.
Photodiodes sensors to indicate the location from
where to read or write.
19. In the magnetic tapes the data are stored in terms
of blocks where each block consists of grouping
of data known as records.
There is some reserved blank spaces called inter-
block-gap (IBG)
When one block contains more than one record, it
is separated by a inter-record-gap (IRG)
Whenever an IRG is reached, the moving tape is
stopped until record is processed.
20. Advantages of magnetic tapes
Hold high recording density, low cost per bit
storage.
Have virtually unlimited storage capacity
Portable, compact in size, lightweight and
removable
Easy to handle and store
Very inexpensive mode of offline data storage
and a large amount of data can be stored in small
storage space.
21. Disadvantages of magnetic tapes
Sequential in nature, not suitable where data is
accessed requires a random order
Slow compared to the magnetic disks
Kept in dust free environment
Away from corrosive gases and chemicals, they
can cause tape-reading errors.
Uses parity bit, hence if minor error occurs, it is
difficult to recover the data.
Not flexible, updating the records is difficult
They wear out.
22. Magnetic disk
They offer high storage capacity and reliability
Has capability to access the storage data directly.
It consists of a plastic/metal circular plate / platter
, which is coated with magnetic oxide layer
Data is represented as magnetized spots
Magnetized represents 1, absence of magnetized
spots represents 0.
To read the data, the magnetized spots on the
disk are converted into electrical impulses, which
are then transferred to the processor.
23. Writing data onto the disk is accomplished by
converting the electrical impulses received by the
processor into magnetized spots on the disk.
The data on the disk can be erased and reused
virtually infinitely.
There is a protective case or cartridge to shield
the disk to protect from dust and other external
interference.
25. Storage organization of a magnetic
disk
Its divided into imaginary tracks and sectors.
Tracks are concentric circle where data are
stored, are numbered from the outermost ring to
inner most ring starting with zero.
Sectors refer to the number fixed-size areas that
can be accessed by one of the disk drive
read/write heads, in one rotation of the disk,
without the head having to change the position.
An intersection of a track and a disk sector is
known as track sector.
26. Generally a disk has eight or more disks sectors
per track.
Disks are marked on both the surfaces, hence
called double-sided disks.
Each sector is assigned a disk address before a
disk drive can access a piece of data.
The disk address comprises a sector number,
track number and surface number
The tracks sectors are grouped into collection
known as cluster.
Cluster is also referred as minimum amount of
disk space used by a single file.
28. Many disks are maintained and used together to
create a large disk-storage system.
All the disks are stacked top of each other with a
common spindle, which rotates them.
There is a gap between each platters, so that
read/write head can perform the operation.
All the read/write of each disks are attached to a
single disk arm assembly.
All the read/write heads are on equal diameter track
on the different platters at one time.
Tracks of equal diameter on different platters form a
cylinder.
29. Accessing data from magnetic
disk
Data in a magnetic disk is recorded on the
surface of the circular tracks with the help of
read/write head, which is mounted on the access
arm assembly.
These heads can be in multiple numbers to
access the adjacent tracks simultaneously and
making a disk faster.
The access arm assembly can be positioned in
both inward and outward directions so that read/
write can move on the horizontal surface of the
disk
In case of multiple disks, each disk surface has
its own read/write head that works in harmony
with other read/write heads to record the data.
30.
31. The process of accessing data comprises of the
following three steps.
Seek
The read/write heads are positioned on the specific
track on disk platter. The time taken in doing so is
known as seek time.
It is the average time required to move the heads to
the desired track on the disk
May range between 2and 15 ms , commonly 9 ms.
32. Rotate
Once the positioned on the desired tracks, the head
of the specific platter is activated.
Since the disk is rotated constantly, the head has to
wait for the required sector or cluster to come under
it.
This waiting time is known as rotational delay time
or latency of the disk.
The rotational latency of disk with 7200 rpm is
4.17ms.
33. Data transfer
The data is transferred to or from the disk to the
primary memory.
The rate at which the data are read per from or
written to the disk is known as data transfer rate.
Measured as kilobyte per seconds.
If the data transfer rate per rotation will be
125x512=64000 bytes
Hence transfer of data in a second is 64000/60 =
6,400,000 bytes or 6.4MB
34. Types of magnetic disks
All the disks come in the form of round platters.
Available in different sizes, shapes and designs.
Some are attached to read/write head assembly
whereas some are available in the form of
removable disks.
Broadly divided as
Floppy disk
Hard disk
Zip disk
37. A floppy disk is round , flat piece of Mylar plastic
coated with ferric oxide and encased in a
protective plastic cover (disk jacket).
It is a removable disk and is read and written by a
floppy disk drive including reading , writing data
onto the disk and rotating the disk.
The disk drive read/write head alters the
magnetic orientation of the particles where
orientation in one direction represents “1” and
orientation in other direction “0”
39. Read/ write operation of floppy disk
Floppy disk has to inserted into the floppy disk
drive
Drive is made up of a box with a slot into which
user inserts the disk
When the user inserts the disk, the drive grabs
the disk and spins inside its plastic jacket
The drive has multiple levers that get attached to
the disk.
One lever opens the metal plate or shutter, to
expose the data access area.
Other levers and gears move two read/write
heads until they almost touch the diskette on both
40. The drive circuit board receives instructions for
reading/writing the data from/to the disk through
FDD controller.
If the data are to be written onto the disk, the
circuit board first verifies that no light is visible
through a small window in the floppy disk
If the photo-sensor on the opposite side of the
FDD detects a beam id light, floppy drive detects
to be write protected and does not allow the
recording of the data
41. The circuit board translates the instructions into
signals that control the movement of the disk and
the read/write heads.
A motor located beneath the disk spins a shaft
that engages notch on the hub of the disk,
causing the disk to spin.
When the heads are in correct position, electrical
impulses create a magnetic field in one of heads
to write data to either the top or bottom of the disk
On reading the data, the electrical signals are
sent to the computer from the corresponding
magnetic field generated by the metallic particle
on the disk.
42. Since floppy disk head touches the diskette, both
media and head wear out quickly .
To reduce wear and tear, personal computers
retract the heads and stop rotation when a drive
is not reading or writing the data.
Next write/ read command is given, there is a
delay of about half a second while the motor
gathers maximum speed.
43. Hard disk
Also called as hard drive or fixed drive
primary storage unit of the computer
It consists of a stack of disk platters that are
made up of aluminum alloy or glass substrate
coated with a magnetic material and protective
layers
They are tightly sealed to prevent any dust
particles, which causes head crash from getting
inside
A hard disk can be internal (fixed) or external
(removable) which can hold huge amount of data.
47. The capacity is the amount of information that a
hard disk can store , measured in bytes.
A typical computer comes with 80-320 GB of hard
disk
Hard disk is measured in terms of access time
A hard disk with lower access time is faster than a
hard disk with a higher access time is slower
49. Read/write operation of a hard
disk
A hard disk uses round , flat disks made up of a
glass or metals which are coated on both sides
with a special material designed to store
information in the form of magnetic patterns.
Each platter has its information recorded in tracks
which is further broken into smaller sectors.
The platters rotate at a high speed, driven by a
special spindle motor connected to spindle.
Special read/write devices are mounted onto
sliders and used either record data onto the disk
or read data from disk
50. The sliders are mounted onto the arms, all of
which are mechanically connected to single
assembly and positioned over the surface of the
disk by the device called actuator.
Each platter has two heads , one of the top of the
platter and one on the bottom, so disk with six
platters would have six surfaces and six heads.
Data is recorded onto the magnetic surface of the
disk in exactly same way as the floppy disk
The surface is treated as array of dot positions
with each domain of magnetic polarization set to
binary 1 or 0.
51. To read data from disk, the operating system first
reads File Allocation Table (FAT) in windows
operating system , at the beginning of the
partition.
This tells the operating system in which sector
and track to find the data and then with this
information, the head can read the requested
data.
The heads in most of the hard disk is slightly
above the surface, the distance between the
head and disk surface is much less compared to
the thickness of human hair.
52. When the head accidently touch the media
because of an electrical malfunction, the surface
becomes scratched.
Any data stored where the head has touched disk
is lost, this is called head crash.
55. Zip disk
Its removable storage device and it has capacity
to store about 100-250 MB of data
Measured at 18x13x4 cm and weighs about half
kg
Its rubber feet to stabilize the unit in either vertical
or horizontal position
The disk is made up of plastic material on which
magnetic oxide particles are coated.
There are two indicator lights, green for power
and amber for disk access.
It has eject button on ON/OFF switch.
56. Is similar in diameter to that of 3 ½ inch floppy but
requires a separate drive to read or write the data
onto the zip disk.
There are different versions of zip disk which can
hold 100,250 and 750 MB of data
A zip disk can store about 70 times more than the
floppy disk
It can be used to store heavy graphics , music or
presentation files,
57. Advantages of magnetic disk
They follow direct access mode for reading or
writing data onto the data files.
Used for both online and offline storage of data
Easily movable from one place to another
because of their small size
Data transfer rate is higher than magnetic tapes.
Due to low cost and high recording densities, cost
per magnetic disk is minimum
The storage capacity is unlimited, as many no. of
disk required can be added.
Less prone to corruption of data
58. Disadvantages of magnetic disk
Must be stored in dust free environment in order
to protect them from crashing down.
Not ideal for devices that requires access
required is of sequential nature rather than direct
or random nature
Expensive than magnetic tapes
More susceptible to breach of security and
access gain to sensitive online disk files from
remote terminals.
59. Optical disk
An optical disk is flat ,circular , plastic disk coated
with a material on which bits is stored in the form
of lightly reflective areas and significantly less
reflective areas.
From which the stored data may be read and
illuminated with a narrow-beam source such as
laser-diode.
These disks are capable of storing a huge
amount of data in limited amount of space.
Consists of a rotating disk coated with a thin layer
of metal that acts as a reflective surface and a
laser bean , which is used to read/write head for
recording the data.
60. Comes in various sizes:
Compact disk (CD)
Digital Versatile Disk (DVD)
Blue-Ray disk (BD)
Each requires a different type of disk drive and a
disk.
CD with 700MB capacity and 12 cm diameter is
popular means of optical storage.
Storage capacity of an optical disk is huge, the
cost per bit storage is very low.
61. Storage organization of an optical
disk
Optical disks consists of a single long track in
spiral .
This track starts from the outer edge and spirals
inward to the centre of the disk
The spiral shape of the tack makes the optical
disk suitable for the storing large block of
sequential data onto it such as music
In case of magnetic disk it is easy to locate
magnetic disk tracks since they are located at
fixed distance from the centre.
These tracks are further divided into small sectors
of the same length, irrespective to the location on
the disk surface
62. With more data recording density , the optical
drives have more complicated mechanism as
compared to the magnetic disk drives.
Rotation speed varies inversely with the radius of
the disk.
The disk moves slowly when data is read near
the edges and moves fast when close to the
centre.
Read/write operation is performed through a laser
beam hence no access arm is required that is
used in case of magnetic disk.
63. In magnetic disk tracks are arranged in the form
of concentric circles, in optical disk the tracks are
in spiral fashion.
Accessing data from concentric circle is slower
than a spiral track
Generally the access time for optical disk is from
10 to 40 milliseconds.
64. Access mechanism In optical
disk
Laser beam technology is used for reading or
writing the data on the disk surface of the optical
disk, uses two laser beam sources of different
intensities.
The greater intensity laser beam is used to write
on the recording surface by turning it ON and
OFF at varying rate so that tiny pits are burnt into
the metal coating of the disk
The lesser intensity laser beam is used to read
the stored data, which is strongly reflected by the
coated surface called land and weakly reflected
by the burnt surface called pit.
The change in pattern is detected by a photo
sensor converted into digital signals.
67. Types of optical disk-Compact
disk
Most popular and cheapest optical disk in the
market
Used for storing music in the form of audio, can
record upto 80min of uninterrupted playing time.
Is shiny, silver color metal disk of 12 cm diameter,
Made up o three layers :
a polycarbonate base through which light can pass
A layer of aluminum
Protective layer of acrylic on the top of it.
68. The pits are normally 0.5 microns wide, 0.83 to 3
microns long, o,15 microns deep.
A CD has one track that spirals from the centre to
outside the edge.
This single track is divided into sectors of equal
length and density, files are stored on these
particular contiguous sectors
Different form of CDs
CD-ROM (compact disk-read only memory)
CD-R (compact disk-recordable)
CD-RW ( compact disk rewritable)
69. A CD-ROM disk comes with prerecorded data by
manufactured and can be read but cannot be
altered.
CD-R allows to record your own data, once
written to it later it cannot be altered.
CD-RW is a disk which is rewritable version of the
CD-R that means it allows writing, erasing and
rewriting of data several times.
The data written onto the CD formats can be read
only with the help of a CD-drive
However, CD-R and CD-RW disks need one
special peripheral known as CD writer or CD
burner.
70. Reading data from CD-ROM
A CD drive reads information from the CD’s spiral
track of pits and lands starting from the centre of
the disk and moving to the outer edge
A light is beamed from semiconductor laser
through the bottom of polycarbonate layer and
the aluminum coating monitors the light being
reflected.
Cd is read through the bottom of the disk, each
pit appears as an elevated bump to the reading
light beam.
Light striking the land areas is reflected normally
and detected by photodiode.
71.
72. As the disk rotates at speed between 200 and
500 rpm, the light bounces off the pits causing the
frequency of the light to change.
The reflected light passes through the prism and
then onto a photo sensor.
Light reflected from a pit is 180 degree out of
phase with the light from the lands, differences in
intensity is measured by the photoelectric cells,
which converts into a corresponding electrical
pulse.
73. Writing a data to a CD
The entire surface of disk is reflective, the laser
can shine through the dye and the reflect off the
gold layer.
For CD-R disk to work , there must be way for a
laser to create a non-reflective area on disk.
CD-R disk, has an extra layer that the laser can
modify.
This extra layer is a greenish dye.
When the data is written , the writing laser heats
up the dye layer and changes its transparency.
This change in dye creates the equivalent of non-
reflective bump.
74.
75. The decomposition of the dye in the pit area
through the heat of laser is
irreversible(permanent)
Once CD-R is written, it cannot be erased o
rewritten
However, CD and CD-R drives can be read the
modified dye as a bump later on.
CD-RW is rewritable because it uses phase
changing material on its recording layer, usually
alloy of silver, tellurium , indium and antimony
metals.
Phase-changing metal its state when heated to a
high temperature and can be converted back to
its original state when the heated at a
76. CD-RW disk, the recording layer has a
polycrystaline structure .
While writing to disk , the laser heats up the
selected areas to very high temperature which
melts the crystals into a non-crystalline
amorphous phase
These areas have lower reflectance than the
remaining crystalline areas.
77. This difference in reflectance helps in reading the
recorded data as in case of CD-R disk
To erase the data, process is called annealing,
during this process the area on the layer that has
been changed to amorphous phase is converted
back to original crystalline state by heating it to a
temperature slightly below the melting point of the
phase changing material.
78. DVD
Also known as Digital video disk
Has seven-fold increase in data capacity over the
CD.
The tracks in DVD are placed closer together,
allows more tracks per disk.
The pits which store data is stored are also lot
smaller.
The minimum pit length of single layer DVD is
0.4microns as compared to 0.834 microns
Laser used in DVD to create pits was of the range
635 to 650 nm.
81. Dvd specification allows the information to be
scanned from more than one layer of DVD simply
b changing the focus of the read laser.
The second layer can be read from inside of the
disk out as well as from the outside in
The second layer of each disk data is recorded
“backwards” ,or in reverse spiral track.
To facilitate the focusing of the laser on the small
pits, manufactures uses a thin plastic substrate
thereby reducing the depth of plastic layer that
laser has to travel to reach the pits.
82.
83. Blu-ray disk
Is an optical storage device, which is used record
and play back high definition video and audio,
images and other kind of data.
Developed by Blu-ray Disk Association (BDA)
It uses a blue violet laser having shorter
wavelength (405nm) than red laser(650nm)
Due to shorter wavelength, the laser can be
focused more precisely on the small spot thereby
resulting in storage capacity 10 times that of
DVD.
84.
85. Available in different forms:
BD-ROM
Comes with pre-recorded content that can only be read
BD-R
It is WORM type disk, where you can record data only
once nut read many times.
BD-RW
It is rewritable
Data can be erased and recorded a number of times in a
same disk
BD-RE
Rewritable disk used for high definition audio/vedio and
television recording
86. Comes in two different sizes: 12 cm and 8 cm
Each disk can have single layer or double layers,
depending on which the data capacity differs.
Storage capacity with single layer disk is 25GB
With dual layer it is 50GB
Storage of mini disk with single layer is 7.8 GB
and dual layer is 15.6 GB
One can edit the programs recorded on the disk
or change their order.
The user can create a playlists of the programs
that is stored on disk , so that can be randomly
accessed.
Allows to write one program while simultaneously
watching another program.
87. Advantages of optical disk
Posses large capacity to store information in the
form of multimedia, graphics and video files.
They can store more amount of data in less
amount of space as compared to magnetic tapes
and floppy or zip disks.
Life span of data on optical disk is more about 10-
20 years as compared to magnetic disks
More recording density
Optical disks are not affected by magnetic field.
Its hard to break or melt, physically strong.
Easily portable due to lightweight and small size
88. Disadvantages of optical disk
Costlier when compared to other devices like
floppy disk or zip disk
Not easy to copy as floppy disk, one needs
software and hardware for writing the disk
They posses low data access speed when
compared to magnetic disk
The drive mechanism is more complicated when
compared to magnetic and floppy disks.
89. Magneto-optical storage devices
It includes basic principles of both magnetic and
optical storage systems.
The system writes magnetically and reads
optically.
It is a plastic or glass disk coated with a
compound (ternary alloy of terium ferric cobalt)
with special properties.
Such materials are easily oxidized, dielectric
barrier layers are used to protect the MO layer
from oxidation.
The barriers together with the reflector coating
acts as an optical signal enhancement.
90.
91. The thin film structure that gives the format its
unlimited re-writability is based on a MO alloy
layer enveloped by a barrier layer on each side.
Available in two formats : 5 ¼ inch and 3 ½ inch
Under the pressure of inexpensive and relatively
fast CD-R and CD-RW , MO drives seem to be
loosing ground.
93. Traditional magnetic recording systems uses currents
induced in the magnetic heads by the changing
magnetic fluxes on the disk surfaces to read the data
Magneto-optical systems use polarized light to read
the data from the disk.
The changes in polarized light occurs due to presence
of magnetic field on the surface of the disk, this is
called Kerr effect, where the polarity of the reflected
light is altered depending on the orientation of the
magnetic particles.
If the beam of the polarized light is shined on the
surface , the light polarization of the reflected beam
will change slightly , if it is reflected from a
magnetized surface
94. If the magnetization is reversed , the change in
polarization is reversed too.
The magnetized areas. That is pits cannot be
seen in regular light, but only in polarized light
The change in direction of magnetization could be
associated with numbers 0 or 1 making this
technique useful for binary storage.
95. Basics of MO recording
Around 200 ºC, every magnetic material loses
magnetization due to a complete disordering of
their magnetic domains, as a result lose the data
stored on them.
Material’s coercivety, is the measure of the
material resistance to magnetization by the
applied magnetic field decreases as the
temperature approaches the curie point, and
reaches zero when the temperature is exceeded.
Materials coercivity drops at higher temperature
allows thermally assisted magnetic recording with
relatively weal magnetic fields.
96.
97. The recording layer is heated by the laser to a
point where its magnetic orientation is dissipated.
As this spot on the disk cools, the new magnetic
orientation-corresponding to the new information
is set by the magnetic head to correspond to “0”
and “1” of digitals signals
To rewrite the data on MO disk, it is necessary to
erase all previous signals before new data can be
recorded.
Two lasers are used to record the data (one to
erase and one to record) or single laser must first
erase the data in first rotation and then record the
data the second time.
98. Universal serial bus
Developed by Intel
Set of connectivity specifications that establishes
communication between personal computers and
devices such as mouse, keyboard, pen drive ,
external hard disk etc
Every computer and laptop comes with one or
more USB ports.
All USB devices come with a USB connector that
is plugged into the USB port on the computer.
As you plug it to the computer, it is detected and
required software is configured automatically, no
need to restart the computer.
100. pen drive
Is a removable storage device that is frequently
used now a days to transfer data such as audio ,
video and files from one computer to another.
it consists of small printed circuit board , which is
fitted inside a plastic , metal or rubber casing to
protect it.
The USB connector is present at one end of the
pen drive is protected by either removable cap or
pulling it back in the casing
Ranges upto 1 GB to 32GB
Fast, robust , reliable, portable, consumes very
less power, no battery required.
102. External hard disk
It is used outside the computer case and
connected to system through USB interfaces in
the PC.
Storage capacity ranges upto 20GB to several
TBs
Compatible with the operating systems that
support interface standards such as USB MSC
(mass storage class) and IEEE 1394
It is reliable and has high capacity storage media
Portable and plug and play feature.
As soon as the hard disk is connected to the
system via USB, it is ready for transferring of
data.
103. Memory stick
Also known as memory card.
Designed to be used in portable electronic
devices such as mobile phones , digital cameras
etc
Launched by SONY and immediately gained
popularity due to its support for fast data transfer
speed and large storage capacity
Started with 128MB , now in market 32GB
memory cards are available
Even a smallest memory card of 4MB can store
about 80 images which is much more than a
standard 3 ½ inch floppy disk. It can be removed
from the portable device and accessed by a
personal computer using memory stick-capable
108. Types of memory stick
Memory stick PRO
Memory stick DUO
Memory stick PRO DUO
Memory stick Pro-HG DUO
Memory stick Micro (M2)
Memory stick PRO
Introduced in 2003- by SONY and SCANDISK
Provides theoretical storage capacity of upto 32GB
It provides 4 bit parallel interface with theoretical transfer
rate of upto 480 Mb/s
Used in megapixel cameras and camcorders.
109. Memory stick DUO
Used for small, pocket-sized devices such as
mobiles phones , music players , digital cameras
etc.
Equipped with magicgate technology that is used to
encrypt data stored on card.
Small in size but costs more
Memory stick PRO DUO
Supersedes the memory transfer rate of memory
stick duo
Provides a larger memory space upto 32GB and
high speed data transfer to/ from the card.
110. Memory card PRO-HG DUO
It has 8-bit parallel interface
Clock frequency of 60 MHZ
Provides high transfer speed of data than memory
stick PRO DUO
Memory stick Micro (M2):
Light , compact storage media
Dimension 15 mmx12.5 mmx1.2 mm
Used for mobile devices
Offers capacity upto 16MB to 32GB
Transfer rate of 160 Mb/s
111. Mass storage devices
In order to have large amount of storage, a
different kind of storage system is used.
Multiple units of similar kinds of storage media
are associated together to form a chain of mass
storage devices.
These may include multiple magnetic tape reels
or cartridges , multiple arrays of magnetic disks or
multiple CD-ROMs as storage device.
Three types:
Redundant Array of Inexpensive Disk (RAID)
Automated Tape library
CD-ROM jukebox
112. RAID
Idea is to combine multiple hard disks into an
array if disk drives to obtain high performance,
large capacity and reliability.
Disk array can be made fault tolerant by using
several techniques such as RAID0,RAID1,…
RAID6
113. Automated tape library
Comprises numerous set of magnetic tapes along
with their drive and controllers mounted in a
single unit.
The unit comprises one or more tape drives to
perform read/write operations on the tape in the
tape library
In tape environment, these tape can be
simultaneously read or written, thus resulting in
the speed transfer of data.
Reliability is increased, if one disk fails, then unit
can continue to operate with other drives.
These tape libraries can store up to several
117. CD-ROM jukebox
It comprises numerous sets of CD-ROM disks
along with their drives and controller mounted in a
single unit.
The unit comprises one or more CD-ROM drives
to perform read/write operations on the CD-ROM
in the jukebox,
In multiple CD-ROM drive environment , these
CD-ROM can be simultaneously read or write
resulting in speedy transfer of data
Multiple drives lead to reliability of storage unit
because if one of the drive fails , then the unit can
continue to operate with the other CD-ROM
drives.
