Pratica di Shadowing: System Design: Why is Kafka fast? - Impara a parlare inglese con i video

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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.

Il contesto: Perché Kafka è veloce?

Immagina di guardare un video in inglese che spiega i segreti del sistema Kafka, focalizzandosi su due design choices che lo rendono ultraveloce: l'accesso sequenziale ai dati e il principio di "zero copy". Il dialogo è tecnico ma chiaro, con esempi concreti (come il tubo per il liquido o i dischi rigidi) che aiutano a capire concetti complessi. E' il tipo di video perfetto per esercitare l'ascolto e la pronuncia, perché combina lingua tecnica con spiegazioni semplici.

Frasi e collocazioni utili da memorizzare

  • "optimized for high throughput": ottimizzato per un alto throughput (capacità di trasmissione). Utile in contesti tecnici o quando si parla di prestazioni.
  • "append only log": registro di sola append. Una struttura dati chiave in Kafka, che aggiunge nuovi dati alla fine del file.
  • "eliminate excess copy": eliminare le copie in eccesso. Un concetto importante nel "zero copy", per trasferire dati senza sprechi.
  • "order of magnitude faster": più veloce di un ordine di grandezza. Per esprimere differenze enormi tra prestazioni.

La tua sfida shadowing: Ripeti e imita!

Ora è il tuo turno: usa il metodo shadow speak per esercitarti. Riproduci un frammento del video (5-10 secondi), poi metti in pausa e ripetilo immediatamente, cercando di imitare l'intonazione, la velocità e la pronuncia. Concentrati su frasi come "Sequential access is several order of magnitude faster" o "Kafka is optimized for high throughput". Se fai un errore, non ti preoccupare: ripeti il processo finché non senti che la tua pronuncia è più fluida. Un shadowing site o un semplice player video con pausa possono aiutarti a esercitarti in modo efficace. Ricorda: l'obiettivo è non solo capire, ma anche parlare come un madrelingua. Con la pratica, i concetti tecnici diventeranno familiari e la tua confidenza in inglese salirà di livello. Shadowspeaks è la chiave per trasformare l'ascolto in parola!

Cos'è la tecnica dello Shadowing?

Shadowing è una tecnica di apprendimento delle lingue supportata da studi scientifici, originariamente sviluppata per la formazione dei traduttori professionisti e resa popolare dal poliglotta Dr. Alexander Arguelles. Il metodo è semplice ma potente: ascolti un audio in inglese di madrelingua e lo ripeti immediatamente ad alta voce — come un'ombra che segue il parlante con un ritardo di solo 1–2 secondi. A differenza dell'ascolto passivo o degli esercizi di grammatica, lo shadowing costringe il tuo cervello e i muscoli della bocca a elaborare e riprodurre simultaneamente i modelli di discorso reale. La ricerca dimostra che migliora significativamente la precisione della pronuncia, l'intonazione, il ritmo, il discorso connesso, la comprensione dell'ascolto e la fluidità del parlato — rendendolo uno dei metodi più efficaci per la preparazione alla prova di speaking dell'IELTS e per la comunicazione reale in inglese.