There are a few interesting scenarios to keep in mind when writing applications (not just databases!) that read and write files, particularly in transactional contexts where you actually care about the integrity of the data and when you are editing data in place (versus copy-on-write for example). We'll go into a few scenarios where the following can happen: Data you write never actually makes it to disk Data you write get sent to the wrong location on disk Data you read is read from the wrong l...