“Companies have closed their cloud” is a very big news in recent domestic Internet companies, this event is great for network backup user, on the one hand, users to store large amounts of data need to be migrated to other places, on the other hand we are choosing a network backup products will leave sequela, because the rest of the few companies were closed under a lot of uncertainty in the future.

Before this, we is a love-hate relationship for network backup products, love because the use of this application scene everywhere, it is your electronic device extension of the space, you can upload photos at ordinary times on the network location, if your phone has a capacity of enough, it can help you to backup, but if you only 16 gb of storage space, it can also help you make the extra space; It also acts as a bridge between your work computer and your home computer, allowing you to seamlessly switch between different environments through data synchronization…

When it comes to hate, inevitably mention of privacy concerns, this fear comes from two aspects, one is a network backup companies may be attacked by hackers, cause the outflow of their own data and the second is the company in order to obtain more profits began to abuse, such as the analysis of user privacy data for users, and “sell” to other business, etc. Coupled with the possibility of bankruptcy, it seems that we can no longer use the web disk happily.

The world is definitely getting better and better. The potential harm brought by monopoly and vicious competition to users will eventually be solved in the Internet world. The outbreak of blockchain technology is an obvious trend, which enables the transfer of trust between two users to be more similar to the real world without the guarantee of a third party. Sia network is a decentralized P2P network. Files you upload to Sia are encrypted to ensure data privacy. Sia’s smart contract through blockchain ensures 99.99% availability of files you upload. So you don’t have to worry about it going out of business and exposing you to the risk of data loss.

See Sia this project, I was very excited, because it is not only a “better world”, at the same time, it produced a lot of memories for me, I used to work in the thunderbolt 5 years time, if I had to evaluate the company, it must be a creative company, I do the first project in the thunderbolt, is actually “Sia”, We call it DCDN (Distributed CDN), which means that before 2009, that is, before the birth of Bitcoin, Xunlei had such a “grand” idea: we hope to use all the idle disks in the world for everyone to use. You can understand that in the sharing economy at its peak, we’ve been working on a shared disk for 10 years.

I started this project twice and failed, and it was also a shadow in my heart, so that when I started it for the third time, I had already fled far away, afraid to touch it for fear of being hit again. Has a powerful ability of human beings is easy to forget the past pain, we often say “the pain is forgotten where gain follows” it is for this reason, so when I recalled that he recently ten years of work career, I asked myself ever encountered insurmountable difficulties, I will not hesitate to answer “no”, because deep down I think the so-called technical problems, is actually a piece of paper, You don’t know it because you haven’t cracked it yet. But when I discovered Sia, I realized that I was wrong. I should not have abandoned this failure in the past. If I did not face it, I would not have grown from it and realized the true value of Sia.

Based on my understanding of Sia, I concluded that there were two main reasons for the failure of previous projects:

  1. Lack of a “smart contract” between users

  2. Ten years ago consumers did not form the habit of paying

Smart contracts are at the heart of blockchain applications, and in Sia, these contracts mainly include

  1. Space contributors who download a file form a contract to keep the file for a specified period of time in return for a certain amount of money

  2. Contributors are required to submit a deposit: if they fail to complete the contract, not only will they not be paid, but they will lose their deposit.

  3. Contributors who falsify or falsify data will incur significant monetary penalties.

  4. Contributors are penalized if the online rate falls below 95%

  5. Users pay a monthly fee for the space, which is used to pay contributors to the space

Blockchain technology ensures that contracts are properly executed, so that contributors to the space “operate” according to the rules, and users can safely store private files on the network. The biggest challenge in p2p file system lies in how to guarantee the availability of the file, because you can’t predict a storage node online time, if a node is not online, then represent stored in the data is not available at the moment, in order to improve availability, you must do the redundant backup, and the difference between a centralized storage system, De-centralization typically takes a long time to make redundant backups, so the system has to be redundant in advance, or do more redundancy.

Smart contracts guarantee this, so Sia boasts 99.99% availability. If you know anything about technology, you might think they’re bragging, because 99.99% is not easy to do in a centralized system. How can you do that with decentralization? And just to verify that, I actually did the math yesterday, and it turns out that, from a probability point of view, you can get this high availability, and here’s how it works, and if you think it’s a little boring, you can skip to the table at the end

By default, Sia splits a file into 10 blocks and copies two copies of each block. That is, a file has 30 blocks in the Sia network. It uses Erasure Coding encryption, which allows you to restore the entire file by taking any 10 blocks. As long as 10 are online, you can download this file. At this point, the problem of file availability becomes a problem of probability, which is required to first classify, and then compute its probability step by step for each category

Classification means, “at least 10 online,” which means we need to figure out 10, 11, 12… , the probability of 30 nodes coming online at the same time, and then summing them; Step by step means that, for each probability, the following steps are used, taking 10 nodes as an example

  1. Select 10 of the 30 nodes

  2. Find the probability that 10 nodes are online at the same time

  3. Find the probability that the other 20 nodes are not online at the same time

At this point, we can list the formula of the probability according to the principle of classification summation and step-by-step product (here we assume that the smart contract can make the online rate reach 90%) :

Since I don’t know how to calculate this easily, I ended up doing it in Numbers. The result is as follows:

As expected, 99.99… %.

The above is my understanding of Sia, I think it has long-term value, secretly tell you, this product has grown more than 100 times since its launch last year, if you agree, you can buy some as an investment (please remember, the final decision is yours), don’t blame me for not telling you oh.

Finally, welcome to exchange.

I am a full stack engineer and live in Shenzhen

I believe in the philosophy of simplicity and value personal growth

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