The core technology of blockchain: distributed ledger

1. First of all, we can take a look at the official website explanation of blockchain technology. In a narrow sense, blockchain is a kind of chain data structure that combines data blocks in a sequential way according to the time sequence, and it is a distributed account book that can not be tampered with and forged by means of cryptography
broadly speaking, blockchain technology is a new distributed infrastructure and computing paradigm, which uses blockchain data structure to verify and store data, uses distributed node consensus algorithm to generate and update data, uses cryptography to ensure the security of data transmission and access, and uses intelligent contract composed of automated script code to program and operate data
as we all know, blockchain technology is an independent underlying architecture from bitcoin system. From the perspective of architecture model, it is a set of distributed ledger, which is naturally used for bookkeeping
in the blockchain technology, if you want to generate accounting records, you need to have the transaction and flow of funds. Therefore, in the initial blockchain technology, the cryptocurrency corresponding to the main network is used as circulation goods, and the circulation transaction records of cryptocurrency between the accounts of the main network of the blockchain will be recorded on the main network
different from other transaction record databases, transaction records on the main network of blockchain technology will be recorded on all block nodes (i.e. all data blocks) in the main network, which is the so-called decentralization principle. That is to say, in blockchain technology, there is no central database to store all records, Every block on the chain has the transaction data of the whole chain, that is to say, every data block is the center
another feature of blockchain technology is that it can't be tampered with, because every transaction on the blockchain will be recorded in all blocks on the chain, so no single data block can change the record. Even if you change it, all other data blocks will also record real data, and each group of data can be traced back to the first time
because of these characteristics of blockchain technology, after the advent of bitcoin, blockchain has also attracted a lot of attention, and many people also began to want to use blockchain technology to make a centerless, traceable and unchangeable data, so as to ensure the credibility of the data
however, blockchain technology also faces many problems, such as single application scenario, non modifiable original error data, non recoverable currency stolen by hackers, etc.

2. That's a good question. Let me give you an example. For example, when I deposit 100 yuan in the bank, the data of this deposit is only recorded in the bank's database, which can't be obtained by others, namely "central bookkeeping". The blockchain is a distributed accounting, a new information recording technology, and it is "encrypted" and "distributed". The data does not exist in a center, but is stored once on the computer of the whole network. For example, if I transfer 100 yuan to you, I will shout to all the computers in the whole network. Let's record the accounts together, that is, "Distributed Accounting".

3. Bookkeeping means mechanisms such as distributed bookkeeping, collective agreement and intelligent consensus. Blockchain technology presents information processing characteristics such as centralization, open sharing, authenticity and reliability, which has aroused increasing attention and application in the financial field, especially in the field of Internet finance. There are many blockchain system development companies. Blockchain technology development enterprises like Renren chain are reliable. You can learn more about them

4. For the benefits, jinwowo feels that the biggest benefit is to obtain great security. First of all, there is a central ledger, so it cannot be destroyed. As like as two peas, each node is only part of the system, and each node has the same rights. Destroying some nodes has no effect on the system at all. Secondly, you can't cheat, because unless you can control most people's computers in the system to make changes, the system will refer to the opinions of most people to decide what is the real result. As a result, it will find that it is totally meaningless to modify your own account book (because others don't admit it). Secondly, since there is no centralized intermediary, making everything run automatically through preset proceres can not only greatly rece costs, but also improve efficiency. Since everyone has the same account book, it can ensure that the process of account book recording is open and transparent.

5.

From the perspective of technology and architecture, I will tell you my understanding of blockchain in common language

what is blockchain? In a word, blockchain is a storage system. To be more specific, blockchain is a distributed storage system without an administrator and each node has all the data

What are the common storage systems like

first, how to ensure high availability

the common storage system usually uses "rendancy" to solve the problem of high availability. As shown in the figure above, if the data can be copied into several copies and rendant to multiple places, high availability can be guaranteed. The data in one place is hung, and there is data in other places. For example, the master-slave cluster of MySQL is the same principle, and the raid of disk is also the same principle

two points need to be emphasized in this place are: data rendancy often leads to consistency problems

1. For example, in the master-slave cluster of MySQL, there is actually a delay in reading and writing, which means there is a inconsistency in reading and writing in a short period of time. This is a side effect of data rendancy

The second point is that data rendancy often reces the efficiency of writing, because data synchronization also consumes resources. If you add two slave libraries, the write efficiency will be affected. The common storage system is to use rendancy to ensure the high availability of data

so the second question, ordinary storage system, can write more

the answer is yes, for example, take this graph as an example:

in fact, MySQL can do a master-slave synchronization of al masters, master-slave synchronization of al masters, two nodes can be written at the same time. If you want to do a multi room multi live data center, in fact, multi room multi live data synchronization. What we should emphasize here is that multi-point writing often leads to the consistency problem of writing conflicts. Take MySQL as an example, suppose that the attribute of a table is self incrementing ID, then the data in the database is 1234 now. If one of the nodes writes and inserts a piece of data, it may become 5, and then these 5 pieces of data are synchronized to another master node, Before synchronization, if another write node inserts a piece of data, a piece of data with self incrementing ID of 5 will be generated. Then, after the generation, synchronize to another node, and the synchronized data will conflict with the two local 5's after it arrives, which will lead to synchronization failure and write consistency conflict. This problem will occur in the case of multi-point writing

how to ensure consistency in multi-point writing

the reform "Swan class" gives you more technical work

6. The three levels are pyramid type, and several switches are connected below the core layer. If the core ports are not enough, they need to be stacked
our school's core uses Nortel 8610, and the expansion only needs to add interfaces. Generally, the core is tested by moles, and adding ports only needs to add moles instead of stacking
an optical switch can be connected under the core, and several layer-2 switches can be connected under the optical switch, which can also save the core port, rece the cost and increase the network users
the specific situation also depends on whether the ports of your core are enough, as well as the core bandwidth, the number of convergence layers, and so on.

7.

This is a data center switch, which supports virtualization, that is VSU. Configuration reference

core switch 1:

Switch1 # configuration terminal
enter configuration commands, one per line. End with cntl / Z.

Switch1 (config) # switch virtual domain 1

Switch1 (config vs domain) # switch 1

Switch1 (config vs domain) # switch 1 priority 200 -- & gt; The default priority is 100, which is configured as a higher priority. After the VSU is successfully established, it will become the management host

Switch1(config-vs-domain)# exit

Switch1(config)# vsl-aggregateport 1 ------> At least two VSL links are needed, and the reliability of one link is low. When link oscillation occurs, VSU will be very unstable

Switch1(config-vsl-ap-1)# port-member interface TenGigabitEthernet 1/1 ------> Configure VSL link, heartbeat link and traffic channel between VSU active and standby cores

Switch1 (config-vsl-ap-1) ﹥ port member interface tengigabit Ethernet 1 / 2
Switch1 (config-vsl-ap-1) ﹥ exit

core switch 2:

switch2 ﹥ configuration terminal
enter configuration commands, one per line. End with CNTL/Z.

Switch2(config)# switch virtual domain 1 ------> Domain ID must be consistent with the first one

switch2 (config vs domain) # switch 2 ----- & gt; The second device must change its ID to 2

switch2 (config vs domain) ｛ switch 2 priority 150

switch2 (config vs domain) ｛ exit
switch2 (config) ｛ VSL aggregateport 1 ----- & gt; At least two VSL links are needed, and the reliability of one link is low. When link oscillation occurs, VSU will be very unstable

Switch2(config-vsl-ap-1)# port-member interface TenGigabitEtherne 1/1 ------> Configure VSL link, heartbeat link and traffic channel between VSU active and standby cores

switch2 (config-vsl-ap-1) # port member interface tengigabit Ethernet 1 / 2
switch2 (config-vsl-ap-1) # exit