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Comment by dmitriid | Hacker News Reader

> Yes, the blockchain data structure ensures that if you verify the older transactions, the newer transactions on top of it are verified.

That is not enough.

Blockchain is proposed for various things like, for example, land registries. They have to be kept around indefinitely long. In many countries financial institutions are required by law to keep financial transactions around for 4 years. Ans so on.

But yeah, sure, go ahead and remove all historical data "because new transaction is mathematically valid".

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> Blockchain is proposed for various things like, for example, land registries. They have to be kept around indefinitely long. In many countries financial institutions are required by law to keep financial transactions around for 4 years. Ans so on.

If you have a copy of the latest block and the older verified block headers, you can trustlessly verify older blocks that people give you.

> But yeah, sure, go ahead and remove all historical data "because new transaction is mathematically valid".

Archival nodes– nodes that store full history– still exist and are still needed. You can query them from a normal full node and get their blocks.

> Archival nodes– nodes that store full history– still exist and are still needed.

Still needed as in "must be there for the chain to function"? Is it possible to have a situation where every node on the chain has truncated its history?

Note also that currently bitcoin needs 300 GB to store data for a fraction of a fraction of transactions needed for the world to run [1]. And crypto enthusiasts people want to move everything onto a blockchain.

[1]

- Total number of transactions is ~640 million: https://www.blockchain.com/charts/n-transactions-total

- Visa alone processes 4.8 billion transactions per quarter: https://s1.q4cdn.com/050606653/files/doc_financials/2020/q3/... which amounts to ~52 million transaction per day

- To handle Visa traffic alone, for that same quarter, Bitcoin blockchain would grow by 9 terabytes. 36 terabytes a year.

And that's for Visa volumes alone. Even though Visa is the biggest one, there's the long tail as well.

"the total number of general purpose credit card transactions in the U.S. was 40.9 billion in 2018" https://www.creditcards.com/credit-card-news/market-share-st...

So, how long before even the archive nodes start truncating data?

Then participants who are obligated to keep 4 years of history around will run nodes that keep that data around.

Will they?

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