"being full node" vs."being sync" : Are they the same?

Question

When we try to be sync using Parity or geth, Does it mean that we are trying to be a full node ?

And is it correct to say that:

being sync = being a full node = keeping the entire blockchain ?

Answer 1

Ethereum and its clients knows a few modes of syncing.

There is "full", "light" and "fast" according to the geth docs.

Only with "full" you actually download and validate everything.

This post explains it.

Basically the faster the node spins up, the less validation is done to retrieve state.

Parity has for itself a few implementations of operation.

Their docs can be found here

Parity is a light client which means by default it does not serve as a full node.

This means

parity kinda corresponds to geth --light.

And both of those mean that state is being reconstructed by validating less deep (more or less).

parity --warp is similar to geth --fast in performance, altough for Parity this means the client looks for data from another full node and simply trusts it while Geth will retrieve state by simply pulling hashes from blocks instead of the whole block. It is being discussed here.

Starting Parity in "warp-mode" means the current state is read from some trusted snapshot:

https://wiki.parity.io/Getting-Synced.html

You can read more about warp here!

Every 5,000 blocks, nodes will take a consensus-critical snapshot of that block’s state. Any node can fetch these snapshots over the network, enabling a fast sync.

This can all be a little confusing. One parameter in Parity says what is validated while another decides when is being validated.

Then there is the --mode option which configures when Parity syncs. This decides at which times the program on your PC operates and syncs

--mode=[MODE]
    Set the operating mode. MODE can be one of: last - Uses
    the last-used mode, active if none; active - Parity
    continuously syncs the chain; passive - Parity syncs
    initially, then sleeps and wakes regularly to resync;
    dark - Parity syncs only when the JSON-RPC is active;
    offline - Parity doesn't sync. (default: last)