There seems to be a very strange problem with racer and lustre over zfs.
When you run SLOW=yes REFORMAT=yes FSTYPE=zfs DURATIOn=2700 sh racer.sh
the dd stuff at the start of racer mostly never finish by themselves, even though we see heavy activity of zfs threads and some errors about ENOSPC in the logs.
the actual creates and other stuff usually gets run after the timeout is already finished and everything is being killed.
Contrast this with an ldiskfs run whre shortly after start we get a lot of messages about "file_create: SIZE=XXX" going all the way until the time is up.
Alex is already looking into this one.