Transcript Storage and Multimedia Part III

Storage and Multimedia Part III
Bayram Güzer
Flash Drive
• A flash drive is a storage device that uses flash
memory.
• Flash memory is non-volatile(kalıcı).
• It can be electrically erased and
reprogrammed.
• In this case it becomes Electrically Erasable,
Programmable Read-Only Memory that is
referred to as EEPROM.
Flash Drive
• Flash memory is solid-state that is nothing in
its is mechanical, everything is entirely
electronic.
• Flash memory has a grid of columns and rows
and a cell having two transistors at each of the
points of intersection of the grid.
• Flash memory is used for the easy and speedy
storage and transfer of information.
How does a flash drive work?
• A flash drive has to be inserted in the USB port on the
computer.
• Latest operating systems detect the flash drive and
install the necessary drivers on their own.
• Once the device is detected, it can be used for storing
the data.
• The device needs to be ejected from the computer. The
system prompts you when it is safe to remove the flash
drive. It can be physically ejected then.
• A flash drive consists of a PCB, a printed circuit board.
It is covered in a plastic or rubber casing, making it
strong.
How does a flash drive work?
• During the early years of the evolution of flash
drives, the devices used could not survive too
many erase cycles.
• The devices of modern times are made to
survive a larger number of erases.
• Flash drives especially find utility in running
lightweight operating systems in order to turn
personal computers into network appliances.
How does a flash drive work?
• In such cases, flash drives contain the operating system
and are used to boot the system.
• Moreover, a flash drive is small in size and portable.
• They enable a speedy transfer of data with less
difficulty.
• Mostly they are plug and play devices.
• They demand no special training to be used.
• Flash drives have a large memory store, larger than
memory capacities that floppies or CDs have.
Types of Flash Drive
• Flash drive can be investigated in three
aspects.
– USB flash drive
– Solid-state drive
– Memory cards that employ flash memory.
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xD Picture Card
Compact Flash
Memory Stick
Secure Digital
Flash Memory
• Flash memory is known as a solid state
storage device, meaning there are no moving
parts -- everything is electronic instead of
mechanical.
• Flash memory is a type of EEPROM chip,
which stands for Electronically Erasable
Programmable Read Only Memory.
Flash Memory
• Flash memory works much faster than
traditional EEPROMs because instead of
erasing one byte at a time, it erases a block or
the entire chip, and then rewrites it.
• It has a grid of columns and rows with a cell
that has two transistors at each intersection.
Flash Memory
• Two types of flash memory is common.
– NAND type.
– NOR type.
• The high density NAND type read in (smaller)
blocks, or pages, while the NOR type allows a
single machine word (byte) to be written
and/or read independently.
Flash Memory
• The NAND type is primarily used in memory
cards, USB flash drives, solid-state drives, and
similar products, for general storage and
transfer of data.
• The NOR type, which allows true random
access and therefore direct code execution, is
used as a replacement for the
older EPROM and as an alternative to certain
kinds of ROM applications.
Flash Memory
• Example applications of both types of flash
memory include
– personal computers, PDAs, digital audio
players, digital cameras, mobile
phones,synthesizers, video games, scientific
instrumentation, industrial robotics, medical
electronics, and so on.
Flash Memory
• In addition to being non-volatile, flash
memory offers fast read access times.
• It is highly durable that it is being able to
withstand high pressure, temperature,
immersion in water etc.
How Flash Memory Saves a File
• Flash-based drives are thinner, faster and
nearly permanent(kalıcı).
• Like a traditional hard drive, a flash-based
drive stores information in the computerreadable language of 0s and 1s.
• But instead of writing data by flipping
magnetic poles on a spinning disk, flash
memory just shuttles electrons around on a
stamp-size microchip.
How Flash Memory Saves a File
• With no moving parts (except, the electrons),
a flash drive requires less power and is more
durable than an ordinary hard drive.
• It can even survive if dropped from the top of
a building but a hard drive can wipe out your
data if its mechanical arm scratches its disk.
How Flash Memory Saves a File
These scanning electron microscope images zoom 10,000x
on a flash drive.
How Flash Memory Saves a File
• Flash memory stores 0s
and 1s in millions of
miniature transistors,
each 1,000 times as thin
as a human hair.
• If the transistor conducts
current, the chip reads it
as 1; if not, it’s 0.
• The current flows just
underneath the transistor
along the chip’s base [A].
How Flash Memory Saves a File
• When the chip is empty,
all transistors are set to 1.
• But when you hit “save,”
the chip records data by
blocking the current to
some transistors, turning
them into a 0.
• To do so, the chip briefly
applies 20 volts to a piece
of silicon called a control
gate [B].
How Flash Memory Saves a File
• This pulls electrons onto
another silicon bit
called a floating gate
[C], leaving a positively
charged area directly
below—and breaking
up the usual path of
electrical current.
How Flash Memory Saves a File
• The only way to move
the electrons and
change the pattern of
1s and 0s—thereby
changing your data—is
by applying precise
voltages to the
transistors.
Limitations
• Block erasure
– One limitation of flash memory is that although it can be
read or programmed a byte or a word at a time in a
random access fashion, it can only be erased a "block" at a
time.
• Memory wear (eskime)
– Another limitation is that flash memory has a finite
number of program-erase cycles (P/E cycles).
– Most commercially available flash products are guaranteed
to withstand around 100,000 P/E cycles, before the wear
begins to deteriorate the integrity of the storage.
– Micron Technology and Sun Microsystems announced an
SLC NAND flash memory chip rated for 1,000,000
P/E cycles on December 17, 2008.
Limitations
• Read Disturb
– The method used to read NAND flash memory can
cause other cells near the cell being read to
change over time if the surrounding cells of the
block are not rewritten. This is generally in the
hundreds of thousands of reads without a rewrite
of those cells.
USB Mass-Storage Device Class
• The USB mass storage device class, otherwise
known as USB MSC or UMS, is a protocol that
allows a Universal Serial Bus (USB) device to
become accessible to a host computing
device, to enable file transfers between the
two.
• To the host device, the USB device appears
similar to an external hard drive, enabling
drag-and-drop file transfers.
USB Mass-Storage Device Class
• The USB mass storage device class comprises a
set of computing communications protocols
defined by the USB Implementers Forum that run
on the Universal Serial Bus. The standard
provides an interface to a variety of storage
devices.
• Devices which support this standard are referred
to as MSC (Mass Storage Class) devices. While
MSC is the official abbreviation, UMS (Universal
Mass Storage) has become common in online
jargon(argo).
USB Mass-Storage Device Class
• Some of the devices that are connected to computers via
this standard include:
– external magnetic hard drives
– external optical drives, including CD and DVD reader and writer
drives
– portable flash memory devices
– adapters bridging between standard flash memory cards and
USB connections
– digital cameras
– various digital audio players and portable media players
– card readers
– PDAs
– mobile phones
USB Implementers Forum
• The USB Implementers Forum (USB-IF) is a
non-profit organisation to promote and
support the Universal Serial Bus.
• It was formed in 1995 by the group of
companies that developed USB.
• Notable members include Apple Computer,
Hewlett-Packard, NEC, Microsoft, Intel, and
Agere Systems.
SuperSpeed USB (USB 3.0)
• SuperSpeed USB (USB 3.0) brings significant
performance enhancements to the ubiquitous
USB standard, while remaining compatible
with the billions of USB enabled devices
currently deployed in the market.
• SuperSpeed USB (USB 3.0, 5 Gbit/s) will
deliver 10x the data transfer rate of Hi-Speed
USB (USB 2.0, 480 Mbit/s), as well as
improved power efficiency.
USB Flash Drive
• A USB flash drive is a data storage device that consists
of NAND-type flash memory with an integrated
Universal Serial Bus (USB) interface
• USB flash drives are often used for the same purposes
for which floppy disks or CD-ROMs were used.
• They are smaller, faster, have thousands of times more
capacity, and are more durable and reliable because of
their lack of moving parts.
• USB flash drives are typically removable and
rewritable, and physically much smaller than a floppy
disk.
• Most weigh less than 30 g (1 oz).
USB flash drive
• USB Flash drives use the USB mass storage
standard, supported natively by modern
operating systems such as Linux, Mac OS X,
Windows, and other Unix-like systems.
• USB drives with USB 2.0 support can store more
data and transfer faster than a much larger
optical disc drives like CD-RW or DVD-RW drives.
• USB drives can be read by many other systems
such as the Xbox 360, PlayStation 3, DVD players
and in some upcoming mobile smartphones.
USB flash drive
• Nothing moves mechanically in a flash drive
and computers read and write flash-drive data
using the same system commands as for a
mechanical disk drive with the storage
appearing to the computer operating system
and user interface as just another drive.
USB flash drive
• A flash drive consists of a small printed circuit board
carrying the circuit elements and a USB connector,
insulated electrically and protected inside a plastic,
metal, or rubberized case which can be carried in a
pocket or on a key chain, for example.
• The USB connector may be protected by a removable
cap or by retracting into the body of the drive,
although it is not likely to be damaged if unprotected.
• USB flash drives draw power from the computer via
external USB connection.
USB flash drive – Essential Components
1 USB Standard-A plug
provides a physical interface to the
host computer.
2 USB mass storage controller device
a small microcontroller with a small
amount of on-chip ROM and RAM.
3 Test points
for testing during the flash drive's
manufacturing or loading code into
the microprocessor.
4 Flash memory chip
stores data (NAND flash is typically
also used in digital cameras).
USB flash drive – Essential Components
5 Crystal oscillator
produces the device's main 12 MHz
clock signal and controls the device's
data output through a phase-locked
loop.
6 LED
indicate data transfers or data reads
and writes.
7 Write-protect switch (Optional)
indicate data transfers or data reads
and writes.
8 Space for second flash memory chip
provides space to include a second
memory chip. Having this second space
allows the manufacturer to use a single
printed circuit board for more than one
storage size device.
USB flash drive – Essential Components
USB connector cover or cap
reduces the risk of damage,
prevents the entry of dirt
or other contaminants, and
improves overall device
appearance. Some flash
drives use retractable (geri
içeri çekilebilir) USB
connectors instead. Others
have a swivel arrangement
so that the connector can
be protected without
removing anything.
USB flash drive – Essential Components
Transport aid
the cap or the body often
contains a hole suitable
for connection to a key
chain or lanyard(kordon).
Connecting the cap,
rather than the body, can
allow the drive itself to
be lost.
USB Flash Drive
• The storage part of an
EEPROM cell acts like a
permanently-open(ON) or
closed(OFF) transistor.
• Charging is accomplished by
grounding the source and
drain terminals and placing a
voltage on the control gate.
• When the “floating gate” is
charged, it impedes the flow
of electrons from the control
gate to the silicon, and the 0
or 1 is determined by whether
the voltage on the control gate
is blocked or not.
http://www.usbmemorysticks.net/flash-drive-technology
USB Flash Drive
• Now, 0 means a
transistor is off and 1
means it’s on because
the gate is open and
electricity can flow.
• With a regular transistor
the data would be lost
once the power is turned
off because that shuts
down the whole thing
and it stays in the 0
position even when
power is back on.
http://www.usbmemorysticks.net/flash-drive-technology
USB Flash Drive
• A flash memory cell
however saves the data
because it’s basically in a
permanent 1 position.
That’s due to its second
gate, the floating gate,
which enables electricity
to stay trapped between it
and the first gate
• The data can still be erased
though by draining the
electricity out, that’s what
the drain to the right is for.
http://www.usbmemorysticks.net/flash-drive-technology
USB flash drive - Advantages
• Data stored on flash drives is impervious to scratches
and dust, and flash drives are mechanically very
robust making them suitable for transporting data
from place to place and keeping it readily at hand.
• Flash drives also store data densely compared to
many removable media. In mid-2009, 256 GB drives
became available, with the ability to hold many times
more data than a DVD or even a Blu-ray disc.
USB flash drive - Advantages
• Compared to hard drives, flash drives use little
power, have no fragile moving parts, and for most
capacities are small and light.
• Flash drives implement the USB mass storage device
class so that most modern operating systems can
read and write to them without installing device
drivers.
USB flash drive - Disadvantages
• Like all flash memory devices, flash drives can sustain
only a limited number of write and erase cycles before
the drive fails(About 90.5 million writes). This should be a
consideration when using a flash drive to run application
software or an operating system.
• Most USB flash drives do not include a write-protect
mechanism, although some have a switch on the housing
of the drive itself to keep the host computer from writing
or modifying data on the drive. Write-protection makes a
device suitable for repairing virus-contaminated host
computers without risk of infecting the USB flash drive
itself.
USB flash drive - Disadvantages
• A drawback to the small size is that they are easily
misplaced, left behind, or otherwise lost. This is a
particular problem if the data they contain are
sensitive.
• As a consequence, some manufacturers have added
encryption hardware to their drives—although
software encryption systems which can be used in
conjunction with any mass storage medium achieve
the same thing.
USB flash drive - Disadvantages
• Most drives can be attached to keychains, necklaces
and lanyards. The USB plug is usually fitted with a
removable and easily lost protective cap, or is
retractable.
• USB flash drives are more expensive per unit of
storage than large hard drives, but are less expensive
in capacities of a few tens of gigabytes as of 2011
Maximum available capacity is increasing with time,
but is less than larger hard drives. This balance is
changing, but the rate of change is slowing.
Solid State Drives
• The speed of hard drive technology is bound
by physics and mechanics.
• More data is being saved into smaller spaces,
but the overall speed of the drive is still
managed by the speed of the spinning platter.
• In order to get more speed, manufacturers
moved to different technology: flash memory.
Solid State Drives
• The flash memory in an SSD is known as
NAND-flash.
• There are two types:
– SLC (single-level cell): In SLC, each cell of memory
stores one bit.
– MLC (multi-level cell):In MLC, each cell of memory
stores stores two bits.
Solid State Drives
• The SLC cell will respond to a certain voltage:
at one level, the cell is assumed to hold 0; at
another level the cell is assumed to hold 1.
• With MLC, the cell will respond to one of four
different levels of voltage, which we can
denote as 00, 01, 10, and 11.
• With MLC memory, to read a cell you have
four times the number of tests to make, which
takes longer.
Solid State Drives
• The issue is that setting a cell to hold a value
involves two different voltages.
• There’s the programming voltage, which
essentially sets the cell to 0, and there’s the
higher erasure voltage, which sets the cell to
1.
Solid State Drives
• The following scenario,
illustrates how these
gates work: you have
two jars of water
connected by a pipe.
• The pipe has a tap and
one jar is lower than
the other.
Solid State Drives
• Fill the top jar.
• When the top jar is full,
the system is assumed
to store 1.
Solid State Drives
• If you now open the
tap, the water drains
down to the bottom jar.
• This is the programming
system.
Solid State Drives
• If you now open the
tap, the water drains
down to the bottom jar.
• This is the programming
system.
• The system is now
assumed to store 0.
Solid State Drives
• In order to set the
system back to 0, you
have to force the water
back uphill and close off
the tap which is very
hard and that is called
as erasing the system.
• When we are talking
about NAND cells,
programming is easy
and erasing is hard.
Deterioration (Bozulma) of Solid State
Drives
• Forcing electrons back and forth over the
subtrate causes the material to deteriorate.
• This causes cell to breaks down and no longer
being able to store a definable state.
• For an SLC, cell takes around 100,000
programming/erasure cycles.
• For an MLC, cell takes aroung 10,000
programming/erasure cycles.
Overwriting Data in Solid State Drives
• Suppose that you wanted to overwrite a page
with some new data.
• The original page is marked as invalid.
• New version of the page’s date is written in
another page entirely.
• A page has three states:
– Empty; it is erased.
– Used; it contains data.
– Invalid; it used to contain data, but the data is now
out of date and will be erased next time.
Memory Cards
– A memory card or flash card is an electronic flash
memory data storage device used for storing digital
information.
– They are commonly used in many electronic devices,
including digital cameras, mobile phones, laptop
computers, MP3 players, and video game consoles.
– They are small, re-recordable, and able to retain data
without power.
– Commonly used memory cards are XD Picture Card,
Compact Flash, Memory Stick and Secure Digital.
XD Card
• xD-Picture Card is a
flash memory card
format, used mainly in
older digital cameras.
xD stands for Extreme
Digital.
• The cards were
developed by Olympus
and Fujifilm, and
introduced into the
market in July 2002.
XD Card
• xD cards are available in
capacities of 16 MB up
to 2 GB.
• Because of its higher
cost and limited usage
in products other than
digital cameras, xD has
lost ground to SD.
Compact Flash
• CompactFlash (CF) is a mass
storage device format used
in portable electronic
devices.
• Most CompactFlash devices
contain flash memory in a
standardized enclosure.
• The format was first
specified and produced by
SanDisk in 1994.
• The physical format is now
used for a variety of
devices.
Compact Flash
• CompactFlash devices
capacities change from 2
MB up to 128 GB.
• Typical weight is about 10
gram.
• CompactFlash IDE (ATA)
emulation speed is
usually specified in "x"
ratings, e.g. 8x, 20x, 133x.
– For example, 133x rating
means transfer speed of:
133 * 150 kbyte/s =
19,950 kbyte/s ~
20 Mbyte/s.
Memory Stick
• Memory Stick is a
removable flash memory
card format, launched by
Sony in October 1998, and
is also used in general to
describe the whole family of
Memory Sticks.
• In addition to the original
Memory Stick, this family
includes the Memory Stick
PRO, a revision that allows
greater maximum storage
capacity and faster file
transfer speeds;
Memory Stick
• Memory Stick Duo, a smallform-factor version of the
Memory Stick (including the
PRO Duo); and the even
smaller Memory Stick Micro
(M2).
• In December 2006 Sony added
the Memory Stick PRO-HG, a
high speed variant of the PRO
to be used in high-definition
video and still cameras.
• Memory Stick cards can be
used in Sony XDCAM EX
camcorders via the MEADSD01 adapter.
Memory Stick
• Capacity changes from 4 MB to
256 GB.
• As of January 2010, it appears
that Sony is beginning to combine
support for SD/SDHC and
Memory Stick formats in their
products.
• All digital cameras and
camcorders can use SD and SDHC
cards as well as Memory Sticks
announced by Sony at the 2010
Consumer Electronics Show.
• Sony is releasing its own line of
SD cards. Many claim this
development as the end of the
format war between Memory
Stick and SD card.
Secure Digital
• Secure Digital (SD) is a
non-volatile memory card
format developed by the
SD Card Association (SDA)
for use in portable
devices.
• The SD technology is used
by more than 400 brands
across dozens of product
categories and more than
8,000 models, and is
considered the de-facto
industry standard.
Secure Digital
• SC Card Association board
members are;
– Canon Inc., Eastman Kodak
Company, Hewlett Packard,
Industrial Technology Research
Institute, Infineon Technologies
AG, Kingston Technology Company,
Matsushita Electric Industrial Co.,
Ltd., Motorola Inc., NEC
Corporation, Nokia Corporation,
Power Digital Card Co., Ltd.,
Samsung Electronics Co., Ltd.,
SanDisk Corporation, Sharp
Corporation, Socket Mobile, Inc.
and Toshiba Corporation.
• The Standard-Capacity (SDSC)
card family, commonly termed
SD, has an official maximum
capacity of 2 GB, though some
are available up to 4 GB.
Secure Digital
• The High-Capacity (SDHC) card
family have a capacity of 4 GB
to 32 GB.
• EXtended-Capacity (SDXC) card
family have a capacity starting
above 32 GB with a maximum
of 2 TB.
• Weight changes from 0,5 gram
to 2,0 gram.
• The Speed Class Rating is the
official unit of speed
measurement for SD Cards,
defined by the SD Association.
– Class 2: 2 MB/s
Class 10: 10 MB/s
References
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http://www.buzzle.com/articles/how-does-a-flash-drive-work.html
http://www.usbmemorysticks.net/flash-drive-technology
http://computer.howstuffworks.com/flash-memory.htm
http://en.wikipedia.org/wiki/USB_flash_drive
http://en.wikipedia.org/wiki/Flash_memory
http://en.wikipedia.org/wiki/USB_mass_storage_device_class
http://en.wikipedia.org/wiki/USB_Implementers_Forum
http://www.usb.org/developers/ssusb
http://en.wikipedia.org/wiki/CompactFlash
http://en.wikipedia.org/wiki/Secure_Digital
http://en.wikipedia.org/wiki/XD_Picture_Card
http://en.wikipedia.org/wiki/Memory_stick
http://www.popsci.com/node/19967
http://pcplus.techradar.com/2011/05/27/how-solid-state-drives-work/
http://en.wikipedia.org/wiki/Solid-state_drive
http://en.wikipedia.org/wiki/Memory_card