Практика Shadowing: System Design: Why is Kafka fast? - Изучайте разговорный английский по видео

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Why is Kafka fast?
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What is the secret?
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We will talk about it in this video.
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Let's dive right in.
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We'll first start by acknowledging that the term fast is ambiguous.
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What does it even mean that Kafka is fast?
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Are we talking latency?
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Are we talking throughput?
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Is fast compared to what?
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Kafka is optimized for high throughput.
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It is designed to move a large number of records in a short amount of time.
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Think of it as a very large pipe moving liquid.
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The bigger the diameter of the pipe, the larger the volume of liquid that can move through it.
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So when someone says Kafka is fast, they usually refer to Kafka's ability to move a lot of data efficiently.
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What are some of the design decisions that help Kafka move a lot of data quickly?
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There are many design decisions that contributed to Kafka's performance.
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In this video, we'll focus on two.
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We think these two carry the most weight.
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The first one is Kafka's reliance on sequential I.O.
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What is sequential I.O.?
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Let's dig deeper into that.
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There's a common misconception that disk access is slow compared to memory access.
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But this largely depends on data access patterns.
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There are two types of disk access patterns, random and sequential.
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For hard drives, it takes time to physically move the arm to different locations on the magnetic disks.
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This is what makes random access slow.
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For sequential access though, since the arm doesn't need to jump around it is much faster to read
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and write blocks of data one after the other kafka takes
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advantage of this by using an append only log as its primary data structure
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and the pen only log adds new data to the end
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of the file this access pattern is sequential now let's bring
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this idea home with some numbers on modern hardware with an
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array of this hard disks sequential will write reach hundreds of megabytes per second,
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while random writes are measured in hundreds of kilobytes per second.
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Sequential access is several order of magnitude faster.
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Using hard disks has its cost advantage too.
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Compared to SSD, hard disks come as one-third of the price, but with about three times the capacity.
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Giving Kafka a large pool of cheap disk space without any performance penalty, means that Kafka can cost-effectively retain messages for a long period of time,
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a feature that was uncommon to messaging systems before Kafka.
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The second design choice that gives Kafka its performance advantage is its focus on efficiency.
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Kafka has moved a lot of data from network to disk and then from disk to network.
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It is critically important to eliminate excess copy when moving pages and pages of data between the disk and the network.
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This is where zero copy principle comes into the picture.
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Modern Unix operating systems are highly optimized to transfer data from disk to network without copying data excessively.
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Let's dive deeper to see how this is done.
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First, we look at how Kafka sends a page of data on disk to the consumer
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when zero copy is not used at all.
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First, the data is loaded from disk to the OS cache.
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Second, the data is copied from the OS cache into the Kafka application.
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Third, the data is copied from Kafka to the socket buffer.
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And fourth, the data is copied from the socket buffer to the network interface card buffer.
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And finally, the data is sent over the network to the consumer.
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Now this is clearly inefficient.
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There are four copies and two system calls.
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Now let's compare this to zero copy.
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The first step is the same.
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The data page is loaded from the disk to the OS cache.
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With zero copy, the Kafka application uses a system call called send file to
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tell the operating system to directly copy the data from the OS cache to the network interface card buffer.
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In this optimized path, the only copy is from the OS cache into the network card buffer.
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With a modern network card, this copying is done with DMA.
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DMA stands for Direct Memory Access.
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When DMA is used, the CPU is not involved, making it even more efficient.
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To recap, sequential I.O and zero copy principle are the cornerstone to Kafka's high performance.
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Kafka uses other techniques to squeeze every ounce of performance of modern hardware, but these two are the most important in our view.
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If you'd like to learn more about system design, check out our books and weekly newsletter.
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Please subscribe if you learned something new.
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Thank you so much and we'll see you next time.

Почему практиковать речь на этом видео?

Это видео — отличная возможность для практики разговорного английского с естественной речью эксперта. Текст полон профессиональных терминов, но структура простая и логичная, что удобно для shadow speak (метода повторения за говорящим). Вы улучшите понимание технической лексики, научитесь правильно строить сложные предложения и попрактикуетесь в воспроизведении интонации. А ещё здесь много примеров явного сравнения и объяснения, что поможет вам выразить свои мысли ясно и убедительно.

Грамматика и выражения в контексте

  • "What does it even mean that Kafka is fast?" — Структура "What does it mean that..." используется для разъяснения значения фразы. Удобно, когда нужно задать вопрос о смысле абстрактных высказываний.
  • "Kafka is optimized for high throughput" — Пассивный залог "is optimized for" показывает, что действие направлено на достижение определённой цели. Полезно в описании технологий или процессов.
  • "There's a common misconception that disk access is slow" — "There's a misconception that..." помогает исправить ошибочное мнение. Очень удобно в дискуссиях или объяснениях.

Трудные места в произношении

В видео есть несколько слов, которые могут вызвать сложности. Например, "latency" (задержка) произносится как /ˈleɪtənsi/, а не /læˈtensi/. Также обратите внимание на "throughput" (/ˈθruːpʊt/) — здесь "th" произносится как глухой звук, а не как "т". И не забывайте про интонацию в вопросах: в "Are we talking latency?" последнее слово поднимается, что помогает понять, что это вопрос. Для better practice используйте shadowspeaks или shadowing site — повторяйте за говорящим, чтобы улучшить своё произношение и ритм речи.

Что такое техника Shadowing?

Shadowing — это научно обоснованная техника изучения языка, изначально разработанная для подготовки профессиональных переводчиков и популяризированная полиглотом доктором Александром Аргуэльесом. Метод прост, но эффективен: вы слушаете аудио на английском от носителей языка и немедленно повторяете вслух — как тень, следующая за говорящим с задержкой в 1–2 секунды. В отличие от пассивного прослушивания или грамматических упражнений, Shadowing заставляет мозг и мышцы рта одновременно обрабатывать и воспроизводить реальные речевые паттерны. Исследования показывают, что это значительно улучшает точность произношения, интонацию, ритм, связную речь, понимание на слух и беглость речи — что делает его одним из самых эффективных методов для подготовки к IELTS Speaking и реального общения на английском.