Geth --syncmode fast (Deprecated)

geth --syncmode fast

Snap syncing was introduced by version 1.10.0 and was adopted as the default mode in version 1.10.4. Before that, the default was the "fast" syncing mode, which was dropped in version 1.10.14. Even though support for fast sync was dropped, Geth still serves the relevant eth requests to other client implementations still relying on it. The reason being that snap sync relies on an alternative data structure called the snapshot which not all clients implement.

You can read more in the article posted above why snap sync replaced fast sync in Geth

See also

• geth --syncmode [ snap (default) | --syncmode full | --syncmode light | --syncnode fast (Deprecated) ], op-node --syncmode
• geth [ account | console | snapshot | --authrpc.addr | version | --sepolia | --goerli | --pprof | --http | --syncmode | --mine ] --rpc.evmtimeout | --ethstats | --help, Geth logs, geth logs WARN, Log.Error, ports: 8551, 30303, 8547, ~/.ethereum/geth/, --verbosity, --config, geth init, devp2p, p2psim, devp2p, geth dumpconfig