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Comment by antocv | Hacker News Reader

Not everyone, just people who like to run a full node, the others run "light clients" or other variants of light clients, like Electrum, but eventually, if nobody run full nodes it wouldnt work at all.

The bitcoin database size is more than 100GB now in 2017.

Blockchain is used by all altcoins and Namecoin for distributed DNS like system.

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How is it possible then to know your balance? Do you have to go through all the blocks just to find those transactions that involve the public key of your wallet? This sounds extremely impractical, because the majority of the transactions would not involve yourself.

I assume then that there's a way to "query" the blockchain? How does Electrum do it?

What's the rate of growth on the size of the block chain? How big would it be for example after 5 years if 1/100th of economic activity was in BTC?

The rate of growth depends on the amount and size of each transaction people are doing on it. There are methods of pruning or discarding spent transactions, but someone somewhere would have to keep it all.

The amount of transactions people are willing to do depends on the value each does, so some people think if bitcoin transactions are almost free some other people would "spam" the network with their "worthless" transactions, thus increasing/growing the size needlessly. So these people claim high fees should ensure only really valuable transactions happen on the network, and not for buying coffe/payment-processing.

So your other question, astronomical, completely otterly astronomical.

Which is why people invent https://byteball.org and others to solve these problems.

Why would someone need to keep the all? I would think that only the hash would be needed for blocks without UTXO's

That actually brings up the idea of sharding which is to assign a node a specific set of transactions and discard the rest. This allows us not to all need an entire record of the blockchain but implementing that into Bitcoin isn't exactly the easiest.

There's no method for sharding the blockchain today which is considered secure, but it is an active area of research.

You can also run a pruned node, basically you download everything and verify it as you go, but once you've computed the utxo set at a given block, you can throw that block away.

Pruned nodes I think are like 2 GB right now? Something in that ballpark.

I feel it is necessary to mention that there's an enormous amount of snakeoil in the blockchain/appcoin/altcoin industry, and that there are hundreds if not thousands of people who have invented broken "solutions" to blockchain problems that they are trying to sell.

Many of these solutions come from people who genuinely believe that they've solved fundamental problems with Bitcoin. But by and large, they have missed important security vectors. Writing a blockchain is a lot like rolling your own crypto - leave it to the experts, and don't trust one unless you've got a bunch of experts who agree that it seems sound.

These problems are very hard. If you are wondering why Bitcoin has not adopted some interesting new technology despite years of dozens of experts doing their best to get scaling into Bitcoin, it's probably because the interesting new technology has some fatal flaw.

Have a look at this chart, it shows the size of the blockchain:

https://blockchain.info/charts/blocks-size?timespan=all

It now grows linearly because it has reached the maximum block size of 1MB per block (actually 1000 kB) (this is the block size debate you've likely heard about)

Blocks today are almost always 998, 998 kB in size and without a transaction fee your transaction can take multiple blocks to be processed.

Block every 10 minutes (goal) is 6 blocks an hour, 144 blocks a day is 144,000 kB a day, is around 4,320 MB a month.

All the miners run full nodes of course so there's always a bunch of full nodes around.

Most miners operate in a pool and rely on the pool for full node functionality.

Yea that's what I mean. Each mining pool runs at least one full node to support their own mining operation.

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