Ledger 8470000 in JSON format (without inner nodes) is 115 MB large. You can get it if you issue the "ledger" API call on a rippled that you own - it's an admin-only call, as it takes lots of ressources to assemble it.
If you are asking about the size of the databases rippled uses in the backend, these are about 9 GB (ledger headers + validations archive) ~100 GB (transactions) and ~320GB (RocksDB node store, snappy compression enabled) on my node.
Rippled can utilize several backends, the most mature/recommended is RocksDB, a LevelDB adaption by facebook. In general rippled just needs a high performance key-value store for the largest chunk of data (nodes), transactions and other stuff is stored in SQLite databases.