Oh by the way, I saw a nifty patch in the queue :
Find a way to reduce rotational delay when repeatedly writing last WAL page
Currently fsync of WAL requires the disk platter to perform a full
rotation to fsync again.
One idea is to write the WAL to different offsets that might reduce the
rotational delay.
This will not work if the WAL is on RAID1, because two disks never spin
exactly at the same speed...