Is there any way to choose between Archive, Basic, Fast, Light? And whats the benefit of each size of blockchain. Sorry if I said something wrong, I am new. Thank you


You may be mixing terms here.

A blockchain, theoretically speaking, is the history of every transaction that has happened in a given cryptocurrency. There's not a way to choose its size, other than saying what transactions did or did not happen.

What you are probably thinking of is a client. A given program that uses a cryptocurrency has multiple ways of doing so.

A full node is a client that stores the entire blockchain. A full node never needs to ask another node what part of the blockchain is--it already has it all. When a new block is mined, each full node independantly verifies it. However, the disk space usage and other computer resources for a full node continue to increase as the blockchain and network grow.

A light client is a client that stores only part of the blockchain, most likely the headers of the blocks. It doesn't know everything, but it can ask full nodes for what it needs. A system known as SPV allows a light client to trust what a full node tells it--however, in a 51% attack, the light client could be fooled into believing an impossible transaction (i.e. someone spending more than they hand.) Nonetheless, a light client is much easier on a computer, and can easily live on a cellphone.

An archive node is a theoretical term for a client that would store data that even a full node has stopped storing.

There's overlap. For example, a light client could become a full node by downloading more of the blockchain, or be a full node on some parts and light everywhere else.

Here's an analogy: There's one history of the world. However, different books can hold different amounts. A full node is an expensive unabridged encyclopedia. A light client is a history textbook and a library card.

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    Wow "A full node is an expensive unabridged encyclopedia. A light client is a history textbook and a library card." I will remember this analogy. – Xavier Leprêtre B9lab Sep 4 '16 at 22:34
  • This helped me a lot to understand how the cliets work. But can I select between light and full node in geth.exe? Via a command or something? – aneom Sep 5 '16 at 9:03
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    As far as I know, geth is currently full node only, and I don't know if there are any light clients for Ethereum yet. However, light clients are actively being worked on. – Matthew Schmidt Sep 5 '16 at 17:55

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