Secondary Storage Devices. Secondary Storage Device Any type of device that is external to the motherboard and can store data which can be processed by.

Secondary Secondary Storage DevicesStorage Devices

Secondary Storage DeviceSecondary Storage DeviceAny type of device that is external to the motherboard and can store data which Any type of device that is external to the motherboard and can store data which

can be processed by a computer. A secondary storage device's information can can be processed by a computer. A secondary storage device's information can

be easily edited and stays on even when there is no power source. Also, be easily edited and stays on even when there is no power source. Also,

secondary storage devices are not directly accessible by the CPU.secondary storage devices are not directly accessible by the CPU.

The 4 main secondary storageThe 4 main secondary storage devices are:devices are:

- Hard Drives- Hard Drives

- USB Drives- USB Drives

- CDs/DVDs- CDs/DVDs

- SD/miniSD cards- SD/miniSD cards

Hard Drive (Disc)Hard Drive (Disc) The hard drive is the most The hard drive is the most

important secondary storage deviceimportant secondary storage device

It's is the only external storage It's is the only external storage

device that is directly inside the device that is directly inside the

computer and cannot be taken out computer and cannot be taken out

convenientlyconveniently

The computer stores digitally The computer stores digitally

encoded data on rapidly spinning encoded data on rapidly spinning

platters with magnetic surfacesplatters with magnetic surfaces

The seven main parts of a hard drive The seven main parts of a hard drive

today are: the enclosure, the spindle, today are: the enclosure, the spindle,

the spindle motor, the platter, the the spindle motor, the platter, the

actuator arm, the interface and the actuator arm, the interface and the

logic board logic board

Hard Drive ComponentsHard Drive ComponentsEnclosure:Enclosure: The enclosure serves as the case The enclosure serves as the case

for the internal components.for the internal components.

Logic Board:Logic Board: The circuit board that contains The circuit board that contains

the “instruction manual” for a computerthe “instruction manual” for a computer

accessing the hard drive. It “translates” theaccessing the hard drive. It “translates” the

computer’s requests to manage data intocomputer’s requests to manage data into

commands that a hard drive can carry out. commands that a hard drive can carry out.

The logic board also controls all internal functions.The logic board also controls all internal functions.

Hard Drive ComponentsHard Drive ComponentsSpindle Motor:Spindle Motor: The spindle motor is what The spindle motor is what

rotates the platters; it is precisely controlled by rotates the platters; it is precisely controlled by

the logic board. In an average computer hard the logic board. In an average computer hard

drive, the spindle motor spins the platters atdrive, the spindle motor spins the platters at

7,200 or 10,000 RPM (revolutions per minute).7,200 or 10,000 RPM (revolutions per minute).

The motor is attached to the spindle, whichThe motor is attached to the spindle, which

centers and fixes down the platters so that they centers and fixes down the platters so that they

can tolerate the spindle motor’s rapid rotations.can tolerate the spindle motor’s rapid rotations.

Hard Drive ComponentsHard Drive ComponentsPlatter:Platter: A thin glass or A thin glass or

aluminium disc coated with an aluminium disc coated with an

ultra-thin layer of cobalt alloy, ultra-thin layer of cobalt alloy,

which is naturally magnetic. which is naturally magnetic.

Data is organized into outward Data is organized into outward

rings from the spindle.rings from the spindle.

Actuator Arm:Actuator Arm: Controlled by two very strong magnets, the actuator Controlled by two very strong magnets, the actuator

arm writes data onto the platter by aligning the magnetization of the arm writes data onto the platter by aligning the magnetization of the

cobalt alloy surface into patterns which the logic board can recognize. cobalt alloy surface into patterns which the logic board can recognize.

It is also able to read information by deciphering magnetization It is also able to read information by deciphering magnetization

patterns on the platter.patterns on the platter.

OperationOperationHow It Works (Basics):How It Works (Basics):

1. Information is requested from 1. Information is requested from the hard drivethe hard drive

2. The Operating System tells the 2. The Operating System tells the logic board that it wants a filelogic board that it wants a file

3. The logic board commands the 3. The logic board commands the spindle motor to spin the spindle motor to spin the platter(s)platter(s)

4. The actuator arm is moved into 4. The actuator arm is moved into positionposition

5. The logic board uses the actuator arm to decipher information from the 5. The logic board uses the actuator arm to decipher information from the magnetic patternsmagnetic patterns

6. The information is streamed through the interface into the computer’s 6. The information is streamed through the interface into the computer’s RAMRAM

Flash MemoryFlash Memory

A type of memory which does not need a power source to retain its A type of memory which does not need a power source to retain its

contents.contents.

1) As electrons flow through the flash memory device, the device 1) As electrons flow through the flash memory device, the device

physically traps electrons between gatesphysically traps electrons between gates

2) Trapped electrons between two gates are identified as a “one”2) Trapped electrons between two gates are identified as a “one”

3) The electrons are kept between the gates indefinitely3) The electrons are kept between the gates indefinitely

4) Data is erased by releasing electrons from the gates; the cleared 4) Data is erased by releasing electrons from the gates; the cleared

space between the gates is then identified as a “zero”space between the gates is then identified as a “zero”

A USB A USB (universal serial bus)(universal serial bus) is a device that can be is a device that can be

used to transfer information between computers. used to transfer information between computers.

They can be plugged into standard USB ports that They can be plugged into standard USB ports that

are found on most modern computers.are found on most modern computers.

A typical USB A typical USB mass storage mass storage devicedevice

USB Mass Storage DeviceUSB Mass Storage Device

Information about Information about USB Mass Storage DevicesUSB Mass Storage Devices

USB storage devices use flash memory, which is a USB storage devices use flash memory, which is a common type of EEPROM memory common type of EEPROM memory (electrically erasable (electrically erasable programmable read only memory)programmable read only memory), to store information , to store information Once plugged in to a USB port, the device can be installed Once plugged in to a USB port, the device can be installed

quickly without any tools (provided the computer supports quickly without any tools (provided the computer supports the device)the device) USB 2.0 has a maximum transfer rate of 480MB/sUSB 2.0 has a maximum transfer rate of 480MB/s USB devices can be unplugged or plugged in at any timeUSB devices can be unplugged or plugged in at any time

A standard USB portA standard USB port

CompatibilityCompatibility

USB mass storage devices are compatible USB mass storage devices are compatible with any computer that has a USB portwith any computer that has a USB port Virtually every computer made today has 1 Virtually every computer made today has 1

or more USB portsor more USB ports Up to 127 USB devices can be used Up to 127 USB devices can be used

simultaneouslysimultaneously USB devices may have special cables to USB devices may have special cables to

make them compatible with other types of make them compatible with other types of slots, and vice-versa slots, and vice-versa

Examples of USB Examples of USB conversion cablesconversion cables

SD CardSD Card The Secure Digital (SD) card is The Secure Digital (SD) card is

a form of flash memory used in a form of flash memory used in modern digital devices to store modern digital devices to store datadata

Unlike the hard drive, the SD Unlike the hard drive, the SD

card has no moving parts and card has no moving parts and

therefore has more resistance therefore has more resistance

to shock damageto shock damage

SD cards have a locking switch which prevents data from being read, SD cards have a locking switch which prevents data from being read,

written, and deleted from the storage cardwritten, and deleted from the storage card

The standard dimensions of an SD card areThe standard dimensions of an SD card are 32 mm long, 24 mm wide, and 32 mm long, 24 mm wide, and

2.1 mm thick2.1 mm thick

A size comparison of the MiniSD card to an index finger.

MiniSD CardMiniSD Card

The MiniSD card is essentially a The MiniSD card is essentially a

smaller version of the SD cardsmaller version of the SD card

Its compactness is one of the Its compactness is one of the

reasons why it is used in many reasons why it is used in many

portable electronic devicesportable electronic devices

The standard dimensions of a The standard dimensions of a

MiniSD card are 21.5 mm x 20 mm x MiniSD card are 21.5 mm x 20 mm x

1.4 mm1.4 mm

Other Flash Memory DevicesOther Flash Memory Devices

- CompactFlash Cards- CompactFlash Cards

- Memory Sticks (Sony) - Memory Sticks (Sony)

- MultiMediaCards - MultiMediaCards

- SmartMedia Cards- SmartMedia Cards

- xD-Picture Cards- xD-Picture Cards

There are many other flash There are many other flash memory devices. These include:memory devices. These include:

Optical DiscsOptical Discs

Optical discs are flat circular discs that store readable information, Optical discs are flat circular discs that store readable information,

typically in the form of tiny bumps layered in a track on one side of the typically in the form of tiny bumps layered in a track on one side of the

disc. Since the majority of optical disks are not rewritable, they are disc. Since the majority of optical disks are not rewritable, they are

commonly used as permanent storage for things like media files.commonly used as permanent storage for things like media files.

Optical discs Optical discs

Information about Optical DiscsInformation about Optical Discs• There are 3 types of discs: ROM (read only memory), R (Recordable) and There are 3 types of discs: ROM (read only memory), R (Recordable) and

RW (ReWritable)RW (ReWritable)

• A computer reads optical discs by using a laser beam to scan a tiny track A computer reads optical discs by using a laser beam to scan a tiny track

on the discon the disc

• Every time the beam is reflected off the disc, a sensor detects it and the Every time the beam is reflected off the disc, a sensor detects it and the

computer reads a “one”computer reads a “one”

• ROM discs use bumps to reflect the laser beam; these discs are used for ROM discs use bumps to reflect the laser beam; these discs are used for

commercial purposescommercial purposes

Bumps on a Bumps on a

ROM disc ROM disc

Recordable discs use dye to reflect the laser beamRecordable discs use dye to reflect the laser beam

The optical properties of a recordable disc’s dye The optical properties of a recordable disc’s dye

are permanently changed by the heat of the writing are permanently changed by the heat of the writing

laser, resulting in varying reflectivitylaser, resulting in varying reflectivity

The computer uses two lasers for a recordable disc; The computer uses two lasers for a recordable disc;

a strong one for writing on the disc and a weaker a strong one for writing on the disc and a weaker

one for reading the disc so that the disc’s dye is not one for reading the disc so that the disc’s dye is not

further alteredfurther altered

Information about Optical DiscsInformation about Optical Discs

A rewritable disc reflects the reading laser with its phase-change alloy A rewritable disc reflects the reading laser with its phase-change alloy

recording layer, which consists of silver, indium, antimony and telluriumrecording layer, which consists of silver, indium, antimony and tellurium

The phase-change alloy material can switch between amorphous and The phase-change alloy material can switch between amorphous and

crystalline states; therefore, it is rewritablecrystalline states; therefore, it is rewritable

Any area of a RW disc with information on it would be in a crystalline state; Any area of a RW disc with information on it would be in a crystalline state;

in order for the information to be deleted, the area would have to be in order for the information to be deleted, the area would have to be

changed into an amorphous state changed into an amorphous state

A computer must have an infra-red laser beam to be able to read and write A computer must have an infra-red laser beam to be able to read and write

on a RW disc; the laser uses heat to change between the alloy’s states on a RW disc; the laser uses heat to change between the alloy’s states

(400°C for erasing information) (400°C for erasing information)

Information about Optical DiscsInformation about Optical Discs

CompatibilityCompatibility• An optical disc drive is present in almost every An optical disc drive is present in almost every

computer manufactured nowadayscomputer manufactured nowadays

• Due to having different formats, DVDs are not Due to having different formats, DVDs are not

always compatible where CDs arealways compatible where CDs are

•CDs have different sizes but most of them are CDs have different sizes but most of them are

compatible on regular computerscompatible on regular computers

• BluRay discs require a higher density laser, so BluRay discs require a higher density laser, so

they are not compatible with everythingthey are not compatible with everything A BluRay diskA BluRay disk

The Importance of Secondary StorageThe Importance of Secondary StorageSecondary storage devices are important to us because we need some form Secondary storage devices are important to us because we need some form

of storage that can keep data indefinitely. Without secondary storage, you of storage that can keep data indefinitely. Without secondary storage, you

would lose all of your data every time you powered down your computer. would lose all of your data every time you powered down your computer.

External storage devices also provide us with portable forms of non-volatile External storage devices also provide us with portable forms of non-volatile

memory outside of the computer, unlike primary storage.memory outside of the computer, unlike primary storage.

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ReferencesReferences

By Alex Patti and Robin WengBy Alex Patti and Robin Weng