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  • Imagine an airplane flying one millimeter above the ground and circling the Earth once every 25 seconds while counting every blade of grass.

    想像有一台飛機在離地一公釐的位置飛著,並以每 25 秒沿著地球繞行一圈,數著碰到的每株小草的葉片。

  • Shrink all that down so that it fits in the palm of your hand, and you'd have something equivalent to a modern hard drive, an object that can likely hold more information than your local library.

    將這一切縮小到如同你手心大小,它就成了跟一個現代的硬碟相同的東西,而硬碟就是一種可能握有比你當地圖書館更多資訊的物品。

  • 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呢?

  • At the heart of every hard drive is a stack of high-speed spinning discs, with a recording head flying over each surface.

    在每個硬碟的核心有著一疊以高速旋轉的磁碟片,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, and your data doesn't live there in a form you can recognize.

    每片磁碟被蓋上一層微小磁化金屬結晶薄膜,而你的資料並不是以你能辦識的形式存在,

  • Instead, it is recorded as a magnetic pattern formed by groups of those tiny grains.

    取而代之的是,它記錄成一段磁帶,由這一群群極小的結晶形成。

  • In each group, also known as a bit, all of the grains have their magnetization's aligned in one of two possible states, which correspond to zeroes and ones.

    每一群,也稱作一位元(信息量單位),全部的結晶透過磁化作用排列,在兩種可能的狀態相當於 0(低電位勢)和 1(高電位勢)。

  • Data is written onto the disc by converting strings of bits into electrical current fed through an electromagnet.

    透過一個電磁鐵供給,資料藉由轉換位元字串成為電流被寫入磁碟中。

  • This magnet generates a field strong enough to change the direction of the metal grain's magnetization.

    磁鐵產生足夠強度磁場去變換金屬結晶磁化作用的方向。

  • Once this information is written onto the disc, the drive uses a magnetic reader to turn it back into a useful form, much like a phonograph needle translates a record's grooves into music.

    當資料被寫入磁碟時,硬碟使用一個磁性讀取頭將資料轉回成可用格式,就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?

    但如何只透過這些 0 和 1 獲取大量資料呢?

  • Well, by putting lots of them together.

    就是將它們大量地整合在一起。

  • For example, a letter is represented in one byte, or eight bits, and your average photo takes up several megabytes, each of which is 8 million bits.

    舉例來說,一字母代表的是一個位元組或八個位元,而你的照片平均佔了幾個百萬位元組,每個相當於八百萬個位元。

  • Because each bit must be written onto a physical area of the disc, we're always seeking to increase the disc's areal density, or how many bits can be squeezed into one square inch.

    因為每個位元必須寫入光碟的實體區域,我們一直尋找方法增加磁碟表面的密度,或者多少位元可以被壓縮到一平方英寸。

  • The areal density of a modern hard drive is about 600 gigabits per square inch, 300 million times greater than that of IBM's first hard drive from 1957.

    現在的硬碟表面密度大約可以達到每平方英寸六千億個位元,比起 1957 年第一顆 IBM 硬碟還要多了三億倍。

  • This amazing advance in storage capacity wasn't just a matter of making everything smaller, but involved multiple innovations.

    令人驚訝的進步在儲存空間上並不只是把每個元件製作的更小,還致力於多樣的創新。

  • A technique called the thin-film lithography process allowed engineers to shrink the reader and writer.

    一個稱為薄膜平板印刷術工序能讓工程師縮小讀寫頭。

  • And despite its size, the reader became more sensitive by taking advantage of new discoveries in magnetic and quantum properties of matter.

    而除了它的大小,利用在磁性或量子特性新發現的優勢讓讀取頭變得更加敏感。

  • Bits could also be packed closer together thanks to mathematical algorithms that filter out noise from magnetic interference, and find the most likely bit sequences from each chunk of read-back signal.

    位元也被塞得滿滿的,這要感謝數學演算法從磁干擾中濾除了雜訊,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, enabled by placing a heater under the magnetic writer, allowed it to fly less than five nanometers above the disc's surface, about the width of two strands of DNA.

    讀寫頭的熱膨脹控制能在磁性寫入頭下方放置加熱器,讓它可以放在磁片表面上方少於五奈米的距離,大約是兩個標準 DNA 的寬度。

  • For the past several decades, the exponential growth in computer storage capacity and processing power has followed a pattern known as Moore's Law, which, in 1975, predicted that information density would double every two years.

    在過去數十年間,電腦儲存空間和處理功耗呈現指數型成長,這個模式就是大家所知的摩爾定律,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, shrinking the magnetic grains further or cramming them closer together posed a new risk called the superparamagnetic effect.

    但是大概在接近每平方英寸一千億個位元的地方,更進一步地縮小磁結晶或擠滿它們緊靠在一起會產生新的風險,稱作超順磁效應。

  • When a magnetic grain volume is too small, its magnetization is easily disturbed by heat energy and can cause bits to switch unintentionally, leading to data loss.

    當一個磁性結晶的體積變得太小,它的磁化作用很容易地受到熱能的干擾,位元可能會無意中發生切換,導致資料遺失。

  • Scientists resolved this limitation in a remarkably simple way: by changing the direction of recording from longitudinal to perpendicular, allowing areal density to approach one terabit per square inch.

    科學家用一個簡單顯著地方法解決這個限制,就是改變記錄的方向,從縱向改成垂直的,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 through heat-assisted magnetic recording.

    最近,這個潛在的上限已經透過熱輔助磁性記錄再度增加。

  • This uses an even more thermally stable recording medium, whose magnetic resistance is momentarily reduced by heating up a particular spot with a laser and allowing data to be written.

    用一個更加熱穩定的記錄材料,它的磁阻會暫時地減少,透過雷射對一個特別的點加熱,讓資料被寫入。

  • And while those drives are currently in the prototype stage, scientists already have the next potential trick up their sleeves:

    而當這些硬碟現正在原型開發階段時,科學家們已經準備在下一個可能性露一手:

  • bit-patterned media, where bit locations are arranged in separate, nano-sized structures, potentially allowing for areal densities of twenty terabits per square inch or more.

    就是位元模式的傳輸介質,其位元儲存位置被分開排列在奈米大小的結構中,十分有潛力讓表面密度達到每平方英寸二十兆個位元,或更多。

  • So, it's thanks to the combined efforts of generations of engineers, material scientists, and quantum physicists that this tool of incredible power and precision can spin in the palm of your hand.

    所以,這些聯合的工作要感謝每代工程師、材料科學家,及量子物理學家讓這威力驚人和精確的工具能在你的手掌中旋轉。

Imagine an airplane flying one millimeter above the ground and circling the Earth once every 25 seconds while counting every blade of grass.

想像有一台飛機在離地一公釐的位置飛著,並以每 25 秒沿著地球繞行一圈,數著碰到的每株小草的葉片。

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B2 中高級 中文 美國腔 TED-Ed 結晶 平方 硬碟 資料 密度

【TED-Ed】硬碟是如何運作的? (【TED-Ed】How do hard drives work? - Kanawat Senanan)

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    稲葉白兎 發佈於 2021 年 06 月 27 日
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