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  • Imagine an airplane flying one millimeter above the ground

    想像有一台飛機在離地一公釐的位置飛著

  • and circling the Earth once every 25 seconds

    並以每25秒沿著地球繞行一圈

  • while counting every blade of grass.

    數著碰到每株小草的葉片

  • Shrink all that down so that it fits in the palm of your hand,

    將這一切縮小到如同你手心大小

  • and you'd have something equivalent to a modern hard drive,

    而你對於一個現代的硬碟能有一些相同的看法

  • an object that can likely hold more information than your local library.

    這個東西,它很可能地握有比你當地圖書館更多的資訊

  • So how does it store so much information in such a small space?

    所以它如何在一個小空間儲存如此多的資訊?

  • At the heart of every hard drive is a stack of high-speed spinning discs

    在每個硬碟心臟有著一疊以高速旋轉的磁碟片

  • with a recording head flying over each surface.

    每片磁碟表面上方帶有一根記錄頭

  • Each disc is coated with a film of microscopic magnetised metal grains,

    每片磁碟被蓋上一層微小磁化金屬結晶薄膜

  • and your data doesn't live there in a form you can recognize.

    而你的資料變成為你無法辦識的形式存在

  • Instead, it is recorded as a magnetic pattern

    取而代之的是它記錄成一段磁帶

  • formed by groups of those tiny grains.

    由這一群群極小的結晶形成

  • In each group, also known as a bit,

    每一群,也稱作一位元(信息量單位)

  • all of the grains have their magnetization's aligned

    全部的結晶透過磁化作用排列

  • in one of two possible states,

    在兩種可能的狀態

  • which correspond to zeroes and ones.

    相當於0(低電位勢)和1(高電位勢)

  • Data is written onto the disc

    資料被寫入磁碟中

  • by converting strings of bits into electrical current

    藉由轉換位元字串成為電流

  • fed through an electromagnet.

    透過一個電磁鐵供給

  • This magnet generates a field strong enough to change the direction

    磁鐵產生足夠強度磁場去變換方向

  • of the metal grain's magnetization.

    金屬結晶的磁化作用

  • Once this information is written onto the disc,

    當資料被寫入磁碟時

  • the drive uses a magnetic reader to turn it back into a useful form,

    驅動器使用一個磁性讀取頭將資料轉回成可用格式

  • much like a phonograph needle translates a record's grooves into music.

    更像是一部留聲機唱針將唱片的紋路轉成音樂

  • But how can you get so much information out of just zeroes and ones?

    但如何獲取大量資料就只透過這些0和1?

  • Well, by putting lots of them together.

    讓我們整個一起來看

  • For example, a letter is represented in one byte, or eight bits,

    舉例來說,一字母代表的是一個位元組(信息量單位)或八個位元

  • and your average photo takes up several megabytes,

    而你的照片平均佔了幾個百萬位元組

  • each of which is 8 million bits.

    每個相當於八百萬個位元

  • Because each bit must be written onto a physical area of the disc,

    因為每個位元必須寫入光碟的實體區域

  • we're always seeking to increase the disc's areal density,

    我們一直尋找著方法增加磁碟表面的密度

  • or how many bits can be squeezed into one square inch.

    或者多少位元可以被壓縮到每一平方英寸

  • The areal density of a modern hard drive is about 600 gigabits per square inch,

    現在硬碟表面密度大約可以達到每平方英寸六千億個位元

  • 300 million times greater than that of IBM's first hard drive from 1957.

    比起1957年第一顆IBM硬碟還要多了三億倍

  • This amazing advance in storage capacity

    令人驚訝的進步在儲存空間上

  • wasn't just a matter of making everything smaller,

    這不只是把每個元件製作的更小

  • but involved multiple innovations.

    但致力於多樣的創新

  • A technique called the thin film lithography process

    一個稱為薄膜平板印刷術工序

  • allowed engineers to shrink the reader and writer.

    能讓工程師縮小讀寫頭

  • And despite its size, the reader became more sensitive

    而除了它的大小,讓讀取頭變得更加敏感

  • by taking advantage of new discoveries in magnetic and quantum properties of matter.

    利用在磁性或量子特性新發現的優勢

  • Bits could also be packed closer together thanks to mathematical algorithms

    位元也被塞得滿滿。這要感謝數學演算法

  • that filter out noise from magnetic interference,

    從磁干擾中濾除了雜訊

  • and find the most likely bit sequences from each chunk of read-back signal.

    並從磁記憶塊讀取回來的信號中找出最相像的位元序列

  • And thermal expansion control of the head,

    讀寫頭的熱膨脹控制

  • enabled by placing a heater under the magnetic writer,

    能在磁性寫入頭下方放置加熱器

  • allowed it to fly less than five nanometers above the disc's surface,

    讓它可以放在磁片表面上方少於五奈米的距離

  • about the width of two strands of DNA.

    大約是兩個標準DNA的寬度

  • For the past several decades,

    在過去數十年間

  • the exponential growth in computer storage capacity and processing power

    電腦儲存空間和處理功耗呈現指數型成長

  • has followed a pattern known as Moore's Law,

    這個模式就是大家所知的摩爾定律

  • which, in 1975, predicted that information density would double every two years.

    在1975年,預測資料密度將會每兩年成長一倍

  • But at around 100 gigabits per square inch,

    但是大概在接近每平方英寸一千億個位元

  • shrinking the magnetic grains further or cramming them closer together

    更進一步地縮小磁結晶或擠滿它們緊靠在一起

  • posed a new risk called the superparamagnetic effect.

    提出一個新的風險稱作超順磁效應

  • When a magnetic grain volume is too small,

    當一個磁性結晶的體積變得太小

  • its magnetization is easily disturbed by heat energy

    它的磁化作用很容易地受到熱能的干擾

  • and can cause bits to switch unintentionally,

    可能位元無意中發生切換

  • leading to data loss.

    導致資料遺失

  • Scientists resolved this limitation in a remarkably simple way:

    科學家用一個簡單顯著地方法解決這個限制

  • by changing the direction of recording from longitudinal to perpendicular,

    改變記錄的方向從縱向改成垂直的

  • allowing areal density to approach one terabit per square inch.

    能讓表面密度接近每平方英寸一兆個位元

  • Recently, the potential limit has been increased yet again

    最近,這個潛在的上限已經再度增加

  • through heat assisted magnetic recording.

    透過熱輔助磁性記錄

  • This uses an even more thermally stable recording medium,

    用一個更加熱穩定的記錄材料

  • whose magnetic resistance is momentarily reduced

    它的磁阻會暫時地減少

  • by heating up a particular spot with a laser

    透過雷射對一個特別的點加熱

  • and allowing data to be written.

    容許資料被寫入

  • And while those drives are currently in the prototype stage,

    而當這些驅動器現正在原型開發的階段

  • scientists already have the next potential trick up their sleeves:

    科學家們已經準備在下一個可能性露一手

  • bit-patterned media,

    位元模式的傳輸介質

  • where bit locations are arranged in separate, nano-sized structures,

    位元儲存位置被分開排列在奈米大小的結構中

  • potentially allowing for areal densities of twenty terabits per square inch

    十分有潛力讓表面密度達到每平方英寸二十兆個位元

  • or more.

    或更多

  • So it's thanks to the combined efforts of generations of engineers,

    所以這些聯合的工作要感謝每代工程師

  • material scientists,

    材料科學家

  • and quantum physicists

    量子物理學家

  • that this tool of incredible power and precision

    讓這威力驚人和精確的工具

  • can spin in the palm of your hand.

    能在你的手掌中旋轉

Imagine an airplane flying one millimeter above the ground

想像有一台飛機在離地一公釐的位置飛著

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B2 中高級 中文 美國腔 TED-Ed 結晶 資料 平方 密度 硬碟

【TED-Ed】硬盤是如何工作的?- Kanawat Senanan (【TED-Ed】How do hard drives work? - Kanawat Senanan)

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    稲葉白兎 發佈於 2021 年 01 月 14 日
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