Author: village two old
Centralized, decentralized, and distributed comparative analysis. Take epidemic prevention and control as an example.
For friends who have just been in contact with the blockchain, or even industry people who have been in the blockchain for a long time, they are often confused about many concepts in the blockchain. Today, we will explain the three concepts of centralization, decentralization, and distribution from the recent epidemic control as an example.
After the epidemic came out, the state deployed provinces such as Hubei and other provinces to deploy medical resources, modify their vacation time, and took serious measures. This is a centralized approach.
It can be seen that the advantages of the centralized control method is that it is very efficient. The seven days of online crazy spread at home and abroad to build a hospital that can accommodate 1,000 people is one of the efficiency manifestations of this centralized system. The American talk show also came out with the paragraph "Seven days, my net at home is broken, and now a week has passed and it has not been repaired."
At the same time, after the expression of the will of the superstructure, the efficient operation of the provinces and cities in the central network is also an embodiment of centralized and coordinated work.
Distributed collaboration is also well reflected during the epidemic, such as the spontaneous semi-spontaneous promotion of isolation and protection knowledge in various residential communities in different regions, passing the severity of the epidemic and protective measures to residents one by one, and the residents' community at home voluntarily organizing donations Moving to the place where the virus is most severe, even distributed network collaboration. Of course, many readers are still self-isolated in the room, and work collaboratively through the Internet, which is called "distributed office". This is also distributed collaboration.
Through the above examples, it is not difficult for everyone to understand, centralized and distributed.
Let's talk about the blockchain. First understand a few points.
First, a decentralized system is a type of distributed system, and the scope of a distributed system is wider. So some people say that "decentralization is distributed, and distributed is not decentralized." Of course, this statement is not wrong, but it is not clear enough.
Second, there can be centralized applications in a decentralized system, and vice versa, there can be decentralized applications in a centralized system;
Third, decentralization and distribution are not the creation of blockchains. They existed long before the birth of blockchains.
Regarding the above three points, the following will gradually expand and explain.
What are the problems with centralized systems?
Instead of enumerating them one by one like textbooks, give a few simple examples.
For example, the inflation of game currency in a game is very serious. The company decides that the user's suggestions are useless. Unless you decide not to play this game, this kind of inflation is tolerable. If the game company suddenly changes other key fun skills parameters, this user also has no say and there is no reasonable channel to modify it-you cannot vote to decide unless you buy the game company (part of it) and enter the board of directors vote.
For example, quantitative easing in the United States, many people are not satisfied, especially retired elderly people, their purchasing power of money has fallen and become worthless, but their opinions are useless. Similarly, even if other countries have a lot of dollars, such as foreign exchange reserves, they still cannot affect the US quantitative easing policy. Unless you choose to abandon the dollar, the disadvantages of money being worthless cannot be escaped.
Many proponents of the blockchain are dissatisfied with the current centralized governance and eager for a new governance. So there is a so-called decentralization.
Decentralization does not mean that full automation allows the machine to decide everything, and no human intervention is allowed, nor does it mean that the rules that have been formulated cannot be modified, but that the rules need to be modified by a decentralized method. In the blockchain world, mining is used to vote, and currency holders vote to decide. This voting mechanism is also called the consensus mechanism.
Why are distributed systems not necessarily decentralized?
Distributed is not necessarily decentralized. Even if the distributed system runs on hundreds of thousands of servers, it is not necessarily decentralized, such as Baidu, Google's search engine server, all these services belong to these companies. Distributed systems are centralized, not decentralized.
Here is a question for everyone: In January 2009, when Bitcoin appeared, was it decentralized?
No, because at that time Satoshi Nakamoto was mining coins alone, that is, maintaining the network. Decentralized systems must be distributed. Running on only one server, this is not decentralized.
Now it is because there are enough nodes around the world to maintain the network. There are enough users and developers to support and maintain this system.
Centralized applications can run on distributed platforms, and decentralized applications can run.
Centralized platforms can run distributed applications and can run centralized applications.
Take Dapp as an example, most of the so-called decentralized applications are currently operated by a company entity behind, and centralized management. Another example is that Microsoft once allowed users to purchase Windows systems with BTC. This is a payment method that uses a decentralized payment system, namely BTC. If Taobao, Amazon, etc. allow users to use Bitcoin for payment, they also belong to centralized platforms that run decentralized applications. Of course, the alliance chain is also a distributed application. Because the alliance chain is a permission chain made by several dozens of companies, it is also a distributed system, but it is not a decentralized system in the strict sense.
The following involves some computer theory and knowledge of distributed systems, and readers can also learn more about it.
Both Eth and Btc 's systems are transaction-driven distributed state machine systems .
The characteristic of this state machine mode is that all the machines in the system repeat the same set of operations, and there is a certain degree of redundancy to maintain the consistency of the system. In a blockchain system, this redundancy is great. Such a high degree of redundancy or fault tolerance was not common before.
This is not a common mode of operation for distributed systems. In most distributed systems, each machine does a different job, which is faster than a single machine. One machine needs to run for one month, and thirty machines run together, which can be done in one day. This is a theoretical linear addition. In fact, because of task division, communication between various tasks, and then summarize the structure, it may consume 30% 40% of the power consumption in the middle, that is, one machine works for one month to dry. The work that requires 30 machines to work together is not a day, it may take two days to complete. However, it is still more capable than one. Traditionally, such distributed systems are more meaningful.
A state machine is a type of distributed system, but the mode of a state machine is not exactly the same. The first thing a state machine guarantees is not efficiency, but state stability and consistency.
The simple explanation is: a bunch of state machines are not for faster than a machine, but for fault tolerance.
The earliest application of the state machine is on some key and important tasks, such as stock trading, such as traffic system control. These scenarios require that services must be provided continuously without interruption. One minute of downtime is not allowed, and several computers are required to operate simultaneously. In this way, even if one machine is broken, the other can be topped immediately.
Brain hole: For example, after the face wall plan in "Three Body", "Swordman" appeared. The swordman has a button in his hand, and as soon as he presses it, he can destroy both the trisomy and the earth civilization. This is a kind of deterrence. The state machine system must be running behind it. In order to ensure the stability and consistency of the state, otherwise, the first generation of Mr. Luo Ji, the first generation of swordsman, pressed the switch on his hand and found that the system was stuck or did not press the switch. The system thought that something went wrong. When you press the switch, the trouble is big.
This scene can complement the way real-world nuclear weapons operate. No longer.
In the state machine system, as the number of connected machines increases, the efficiency is not linearly increased, but it is slower than a computer because the state is synchronized. This is why some people say that the more full nodes of Bitcoin are not, the better. (About 10,000 Bitcoin full nodes worldwide, 10766 in the afternoon of February 08, 2020)
In traditional application scenarios where state machines are used, the number of machines is not too large (usually single digits), because the more the number, the slower the synchronization. Tens of thousands of full nodes operate simultaneously in Bitcoin, which has never existed before. Therefore, the contradiction between decentralization and efficiency will be talked out all the time.
Blockchain systems such as Eth and btc are not the normal state of distributed systems. Instead, they are special cases. Large-scale computing services cannot be processed using state machines such as blockchains. It is better to use cloud services provided by large platforms. The computing power of the Bitcoin system does not refer to the computing power of cloud services, but the mining computing power.
I hope this article can confuse partners who are confused about centralization, decentralization and distribution.
Happy Lantern Festival. A glass of wine from rivers and lakes, encrypted Erguotou.