Working with the new Linux file system - ext4

Delayed allocation and the zero-length file problem | Thoughts by Ted: "ext3 performs very poorly if applications use fsync a lot; the ordering constraints can mean that if you fsync one file, then large numbers of other files may need to be committed to disk as well." - see first comment

The trick to getting optimum performance seems to be using fsync or fdatasync. We need to implement that, but not before the transition to ext4, otherwise there may be performance penalties.

This article and others on Ted's blog explain the issues well. He is a key architect of these filing systems.