So, all miners have to keep a full copy of the ledger to run stable. Yes, I assumed there was a method like SPV mining since downloading the full ledger takes time and HDD space and it is just certain we are thinking whether we could avoid the unpleasant investment (in time and space) and jump right to the profit part.
Only the IBD takes a lot of time. Syncing back a few hours/days of the blockchain doesn't take that long. It should be reasonable to assume that genuine pools have software (+ backups) running 24/7.
But if I understood right, it did not work out very well so you are strongly advised to download the full copy.
It can cause miners to mine on top of invalid blocks, which causes problems and monetary loss.
I was assuming the same at running nodes that there could be a method to verify transactions...etc. without downloading the full copy. But I guess, it neither works at nodes then. Sooo, both miners and nodes have the full copy of the ledger downloaded, but they have different configurations as for purpose?
You can run a node in pruned mode. This means that you only store a certain amount of MB of raw data (550 is the minimum in Core) + chainstate. However:
1) You still have to download and verify the whole chain.
2) You are no longer a traditional full node, as you don't have the full history and therefore you can't help others to become full nodes.
As far as node configurations are concerned, you can modify a lot of things: Mempool size, Minrelayfee, Only download but not relay blocks with 'listen=0', and so on.
you can choose to run bitcoin core, bitcoin unlimited etc right? you can choose the implementation?
Yes, but be careful with software that isn't properly tested.
I guess another pro is if you want to make your transaction propagate faster Han the already lightning fast speed.
What are you talking about? That is not possible.
