How do hard drives work? - Kanawat Senanan
-
0:07 - 0:11Imagine an airplane flying
one millimeter above the ground -
0:11 - 0:14and circling the Earth
once every 25 seconds -
0:14 - 0:17while counting every blade of grass.
-
0:17 - 0:21Shrink all that down so that it fits
in the palm of your hand, -
0:21 - 0:24and you'd have something equivalent
to a modern hard drive, -
0:24 - 0:28an object that can likely hold
more information than your local library. -
0:28 - 0:33So how does it store so much information
in such a small space? -
0:33 - 0:37At the heart of every hard drive
is a stack of high-speed spinning discs -
0:37 - 0:41with a recording head
flying over each surface. -
0:41 - 0:46Each disc is coated with a film
of microscopic magnetised metal grains, -
0:46 - 0:50and your data doesn't live there
in a form you can recognize. -
0:50 - 0:53Instead, it is recorded
as a magnetic pattern -
0:53 - 0:56formed by groups of those tiny grains.
-
0:56 - 0:58In each group, also known as a bit,
-
0:58 - 1:01all of the grains have
their magnetization's aligned -
1:01 - 1:04in one of two possible states,
-
1:04 - 1:07which correspond to zeroes and ones.
-
1:07 - 1:09Data is written onto the disc
-
1:09 - 1:13by converting strings of bits
into electrical current -
1:13 - 1:15fed through an electromagnet.
-
1:15 - 1:19This magnet generates a field
strong enough to change the direction -
1:19 - 1:21of the metal grain's magnetization.
-
1:21 - 1:24Once this information is written
onto the disc, -
1:24 - 1:29the drive uses a magnetic reader
to turn it back into a useful form, -
1:29 - 1:33much like a phonograph needle
translates a record's grooves into music. -
1:33 - 1:38But how can you get so much information
out of just zeroes and ones? -
1:38 - 1:40Well, by putting lots of them together.
-
1:40 - 1:45For example, a letter is represented
in one byte, or eight bits, -
1:45 - 1:48and your average photo
takes up several megabytes, -
1:48 - 1:51each of which is 8 million bits.
-
1:51 - 1:55Because each bit must be written onto
a physical area of the disc, -
1:55 - 1:59we're always seeking to increase
the disc's areal density, -
1:59 - 2:04or how many bits can be squeezed
into one square inch. -
2:04 - 2:09The areal density of a modern hard drive
is about 600 gigabits per square inch, -
2:09 - 2:16300 million times greater than that
of IBM's first hard drive from 1957. -
2:16 - 2:18This amazing advance in storage capacity
-
2:18 - 2:21wasn't just a matter
of making everything smaller, -
2:21 - 2:23but involved multiple innovations.
-
2:23 - 2:26A technique called the thin film
lithography process -
2:26 - 2:30allowed engineers
to shrink the reader and writer. -
2:30 - 2:33And despite its size,
the reader became more sensitive -
2:33 - 2:39by taking advantage of new discoveries in
magnetic and quantum properties of matter. -
2:39 - 2:43Bits could also be packed closer together
thanks to mathematical algorithms -
2:43 - 2:47that filter out noise
from magnetic interference, -
2:47 - 2:51and find the most likely bit sequences
from each chunk of read-back signal. -
2:51 - 2:54And thermal expansion control of the head,
-
2:54 - 2:58enabled by placing a heater
under the magnetic writer, -
2:58 - 3:03allowed it to fly less than
five nanometers above the disc's surface, -
3:03 - 3:07about the width of two strands of DNA.
-
3:07 - 3:08For the past several decades,
-
3:08 - 3:13the exponential growth in computer
storage capacity and processing power -
3:13 - 3:16has followed a pattern
known as Moore's Law, -
3:16 - 3:23which, in 1975, predicted that information
density would double every two years. -
3:23 - 3:26But at around 100 gigabits
per square inch, -
3:26 - 3:30shrinking the magnetic grains further
or cramming them closer together -
3:30 - 3:34posed a new risk
called the superparamagnetic effect. -
3:34 - 3:38When a magnetic grain volume is too small,
-
3:38 - 3:41its magnetization is easily disturbed
by heat energy -
3:41 - 3:44and can cause bits
to switch unintentionally, -
3:44 - 3:47leading to data loss.
-
3:47 - 3:51Scientists resolved this limitation
in a remarkably simple way: -
3:51 - 3:56by changing the direction of recording
from longitudinal to perpendicular, -
3:56 - 4:01allowing areal density to approach
one terabit per square inch. -
4:01 - 4:05Recently, the potential limit has been
increased yet again -
4:05 - 4:08through heat assisted magnetic recording.
-
4:08 - 4:11This uses an even more thermally
stable recording medium, -
4:11 - 4:15whose magnetic resistance
is momentarily reduced -
4:15 - 4:19by heating up a particular spot
with a laser -
4:19 - 4:21and allowing data to be written.
-
4:21 - 4:24And while those drives are currently
in the prototype stage, -
4:24 - 4:28scientists already have the next potential
trick up their sleeves: -
4:28 - 4:30bit-patterned media,
-
4:30 - 4:35where bit locations are arranged
in separate, nano-sized structures, -
4:35 - 4:40potentially allowing for areal densities
of twenty terabits per square inch -
4:40 - 4:42or more.
-
4:42 - 4:46So it's thanks to the combined efforts
of generations of engineers, -
4:46 - 4:48material scientists,
-
4:48 - 4:50and quantum physicists
-
4:50 - 4:53that this tool of incredible power
and precision -
4:53 - 4:56can spin in the palm of your hand.
- Title:
- How do hard drives work? - Kanawat Senanan
- Speaker:
- Kanawat Senanan
- Description:
-
View full lesson: http://ed.ted.com/lessons/how-do-hard-drives-work-kanawat-senanan
The modern hard drive is an object that can likely hold more information than your local library. But how does it store so much information in such a small space? Kanawat Senanan details the generations of engineers, material scientists, and quantum physicists who influenced the creation of this incredibly powerful and precise tool.
Lesson by Kanawat Senanan, animation by TED-Ed.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TED-Ed
- Duration:
- 05:12
Jessica Ruby edited English subtitles for How do hard drives work? | ||
Jessica Ruby edited English subtitles for How do hard drives work? | ||
Jessica Ruby approved English subtitles for How do hard drives work? | ||
Jessica Ruby edited English subtitles for How do hard drives work? | ||
Jessica Ruby accepted English subtitles for How do hard drives work? | ||
Jessica Ruby edited English subtitles for How do hard drives work? | ||
Jessica Ruby edited English subtitles for How do hard drives work? | ||
Jennifer Cody edited English subtitles for How do hard drives work? |