Running a cron every 30 seconds [closed]

I have a cron job that I need to run every 30 seconds:

*/30 * * * * /bin/bash -l -c 'cd /srv/last_song/releases/20120308133159 && script/rails runner -e production '\''Song.insert_latest'\'''

It runs, but is this running every 30 minutes or 30 seconds?

I've read that cron is not the best tool to run that often. Is there a better tool that I can use on Ubuntu 11.04? Can I fix the above cron?