That would be true except each vnode (by default 64!) has its own backend database. That means with 4 physical nodes each one gets 16 leveldb/bitcask/whatever database backends.

LevelDB's write batching and caching is completely void when thats considered in many circumstances.

Its something that I think Basho should consider changing. Its a trade off of fault tolerance or performance, and I would personally love to see riak go a lot faster.