MongoDB has very nice tunability. The new version ships with journaling turned on by default. You can specify `safe`, which means the data will be written to t

MongoDB has very nice tunability. The new version ships with journaling turned on by default. You can specify `safe`, which means the data will be written to the journal. You can also specify `fsync`, which means additionally the system will issue an fsync on the journal. Additionally, there's the question of the replication protocol, `W` in MongoDB. What I said is that if you turn on `W=2` it will be slow. You should also know that even with `safe` and `fsync` you may lose data if running in `W=1` mode if the master goes down in your replicata set. See my comment above and the reply from a MongoDB guy.