A key feature of Riak KV is the pluggable storage backends. These allow the ability to choose a low-level storage engine that suits specific operational needs. For example, if one needs maximum throughput coupled with data persistence and has a bounded keyspace, Bitcask is a good choice. On the other hand, if one needs to store a large number of keys, then LevelDB would be a better backend recommendation.
These backends are supported:
Riak supports the use of custom storage backends as well. See the storage Backend API for more details.