Trucks full of hard drives, faster than fiber optic? But times have changed!

Many years later, facing the 20MB/s network speed, I thought back to the afternoon when my childhood friend copied the game onto a USB flash drive.

I wonder if you had the same experience as me when you were a kid - because the internet speed at home was very slow, you had to stay online all night to download a game or a movie. Sometimes, when the network was unstable, you even had to download it over several days.

In fact, I have another option. If my neighbor/classmate happens to have the installation package of this game on his computer, I can just take a USB flash drive to his house to copy the game. Manually moving the data may be faster than downloading it from the Internet.

I remember that when I was a kid, the internet speed at home was about 200kB/s, and it took about 2000 seconds, or nearly an hour and a half, to download a 1GB game installation package. But if a neighbor had the installation package, it would take less than 10 minutes to copy the game from the site.

From dial-up to broadband and now fiber-to-the-home, Internet speeds have increased by several orders of magnitude. But today, does physical data transfer still have an advantage over network cables?

Map: Wang Yu; Source: pixabay

A rough analysis shows that there may be some. For example, I ride my bike to and from get off work every day with my computer, which takes about 30 minutes each way. My computer has about 700GB of data, which translates to a data transfer speed of about 400MB/s. In comparison, the usual Internet speed is only 20MB/s, which means that the speed of physical data transfer is 20 times that of a wired network. If I carry a few more hard drives in my backpack when I go to work, or ride my bike faster, the data transfer speed will be even faster.

You may have heard that a truck full of hard drives running on the highway is one of the fastest ways for humans to transmit data. But the speed of optical fiber data transmission is also constantly improving, and its data transmission speed today may exceed your imagination. So, in the competition of transmitting data, which one is better, trucks or optical fibers?

Ultrafast Fiber

In June this year, Japan's National Institute of Information and Communications Technology (NICT) announced that they had successfully achieved a data transmission speed of 402Tbps (1 byte = 8 bits, or 50.25TB/s) on existing commercial single-mode optical fibers, the fastest speed ever achieved using optical fibers. This record is 35% faster than the previous single-mode optical fiber transmission record.

How did they make fiber transmission so fast? This requires us to invite Claude Shannon, the founder of information theory. In 1948, he created a discipline called information theory with a paper. In this paper, Shannon proposed a formula for information transmission speed - C=B∙log₂(1+S/N) . Among them, C is the theoretical upper limit speed of information transmission, B is the channel bandwidth in Hertz, and S/N is the ratio of signal strength to noise strength. Therefore, if you want to speed up information transmission, you need to increase the channel bandwidth and increase the signal-to-noise ratio at the same time.

To understand this formula, let's start with the Wi-Fi I'm using.

My network information

The Wi-Fi signal frequency I am using now is 5GHz, and the bandwidth is 80MHz, which is equivalent to B in the formula being 80×10⁶s⁻¹. The signal power strength received by the computer from the router is (RSSI) -55dBm, and the noise strength is -90dBm. (dBm is a logarithmic power unit, which represents the strength level of the signal relative to 1mW. For every 10dBm increase in the signal, the signal power becomes 10 times the original. For example, 0dBm is equivalent to a power strength of 1mW, 10dBm is equivalent to a power of 10mW, and -10dBm is equivalent to a power of 0.1mW.) In this way, the signal-to-noise ratio S/N=10^(3.5) can be calculated.

Then we can calculate that, in theory, the upper limit of the information transmission speed C between the computer and the router is 924Mbps . However, the actual situation is subject to many conditions such as Wi-Fi encoding mode, computer performance, router performance, etc., and the communication between the computer and the router cannot reach this speed.

Of course, this is just the communication between the computer and the router. The biggest limitation of the Internet speed is how much the company office pays the network operator...

Office internet speed test results.

Back to the latest research results of the National Institute of Information and Communications Technology of Japan, in order to enhance the ability of optical fiber networks to transmit information, they started from the communication principles, increased the communication bandwidth, and improved the signal strength.

Optical fiber has different transmission efficiencies for different wavelengths of light. Only at wavelengths with higher transmission efficiency can optical fiber transmit optical signals better. For light, a specific wavelength range corresponds to a specific frequency range, or bandwidth. The research team said that they used all the low-loss transmission bandwidth in the optical fiber, totaling 37.6THz - worthy of being an optical fiber, the bandwidth is much larger than the 80MHz of wireless signals.

At the same time, they also designed 6 fiber optic signal amplifiers in different bands to enhance signal strength and improve signal transmission capabilities, ultimately achieving a transmission speed of 402Tbps, or 50TB per second.

Schematic diagram of the transmission system. Image source: NICT

What does this speed mean? The capacity of the largest single hard disk on the market is about 20TB, and the fastest optical fiber is equivalent to being able to transmit the capacity of 2.5 large-capacity hard disks per second.

If a truck wants to transmit data faster than optical fiber, it must transport more hard drives in the same amount of time. And trucks generally don’t transport hard drives very fast. For a typical task, it takes at least 1 day, or 86,400 seconds, to disassemble and assemble hard drives and drive on the road.

In these 86,400 seconds, optical fiber can theoretically transmit data continuously at a speed of 2.5 hard disks per second, and the total amount of data transmitted is equivalent to 216,000 hard disks. Therefore, only if the number of hard disks transported by the truck at one time exceeds 216,000, its information transmission speed can be faster than optical fiber.

The mass of a large hard disk with large capacity is about 700 grams, but the vibration during transportation may damage the hard disk, so the hard disk needs to be transported in shockproof packaging. A rough estimate is that after the shockproof packaging, the mass of each hard disk is 1 kilogram. Then the total mass of 216,000 hard disks is 216 tons. my country's truck weight limit is 49 tons. Obviously, a truck with a load of 216 tons is usually not legally allowed on the road.

In other words, the fastest way to transmit data in the world today is optical fiber, not a truck full of hard drives.

Economic Benefits

However, from a practical application perspective, there is still a lot of room for physical transmission of information today.

The speed limit of optical fiber can only exist in laboratories or in the backbone nodes of operator networks. It is very expensive to use these optical fibers to transmit data. Moreover, it is not cost-effective to use a single optical fiber to transmit data. Just like my Internet speed, it is far from reflecting the physical limit, but only reflects the limited funds.

The most typical example is the photo of a black hole. In 2019, the Event Horizon Telescope (EHT) released the world's first photo of a black hole, which was taken using eight millimeter/submillimeter radio telescopes distributed around the world. The raw data of the observation is as high as 4PB (1PB=1024TB), and the data needs to be processed together, but the network speed between the telescope and the data center is not fast enough. In order to process the data together, the fastest option is to express the hard drive full of data to the data center . Don't astronomers want their network speed to be faster? Of course they do, but the cost of building a backbone network is too expensive for them to afford.

However, with the development of technology, the cost-effectiveness of wired networks is also increasing. In 2016, Amazon launched the Snowmobile service that uses trucks to transmit data. This is an 18-wheel heavy truck full of hard drives, and each truck has a capacity of 100PB. But in 2018, a company said that the cost of using this truck was too high, and using a wired network to transmit data might be a more affordable option. In April this year, Amazon cut the project.

But at the same time, Amazon has launched another smaller and more flexible data transmission solution, Snowball EDGE, which is about the size of a suitcase, weighs 22 kilograms, and can store up to 210TB of data. Western Digital has also released a suitcase server that can hold 368TB of data, which can be carried directly in the hand or directly used as a storage server and installed in the computer room.

So, the core of the problem is which method is more popular with real users. At present, it seems that the trucks may be a bit too big to transfer data by physical transportation. But for temporary data transmission needs of hundreds of TB to several PB, direct physical transportation may still be a more affordable option today.

Physical data transportation and fiber optic network transmission each have their own scope of application. Although the advantages of optical fiber are increasing, the physical transportation method still has its own area of ​​expertise.

References

[1]https://www.cnbc.com/2024/04/17/aws-stops-selling-snowmobile-truck-for-cloud-migrations.html

[2]https://www.nict.go.jp/en/press/2024/06/26-1.html

[3]https://interestingengineering.com/innovation/world-record-transmission-optical-fiber

Planning and production

Source: Global Science (id: huanqiukexue)

Author: Wang Yu

Editor: Zhong Yanping

Proofread by Xu Lailinlin

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