> 2) the management of the journal (the write operations in particular) > makes sense?
This one is tricky... The Linux kernel has some thread controls... so the writing has to be done through a single thread... context switch would make some extra IO on disks and performance would suffer... we may eventually need to use two threads.. but bind them to IO... this is hard core... even for NIO (not just libaio). I bet it would make some difference on mapped file as well.
