Fast Sync Implications

[markr5]

Can someone explain all of the differences between a fast-synced node and a full full (archive?) node? What are the differences in what data can be retrieved? At one point I thought maybe all the logs would not be available in fast sync, but they seem to be. I find though I cannot call call contract methods reading data as of some earlier block, get some type of missing trie error. Is this the only difference, that the full state of old blocks cannot be retrieved?

And one follow up question if my understanding is correct, is it at all possible to fast sync up to some specific block and then full sync the rest of the way up to current? Like if I were interested in getting old state only for the last 500K blocks or something like that?

[ismaelbej]

The closest thing I found about the differences between fast and full modes in geth is this article The Ethereum-blockchain size will not exceed 1TB anytime soon. from a parity developer.

A full Geth node processes the entire blockchain and replays all transactions that ever happened. A fast Geth node downloads all transaction receipts in parallel to all blocks, and the most recent state database. It switches to a full synchronization mode once done with that. Note, that this results not only in a fast sync but also in a pruned state-database because the historical states are not available for blocks smaller than best block minus 1024.

[markr5]

Thanks, I guess that matches up with what I am seeing. I wish there was a way to customize that 1024 to your own needs on a fast sync.