As it is now, the broker.id parameter is fixed to -1, which means generate a a new broker.id on startup of the kafka-server. It would be nice if this config could be set to a specific id, because as it is currently, on reboot the kafka broker thinks it is a brand new broker.
Same with the log.dirs config parameter. Since it is fixed to a temporary directory, it will be removed on reboot.
side note: I'll fix this issue myself, and add it as a patch.