Running a cron every 30 seconds

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

Here is what I have:

*/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?

Also, I have been reading that cron might not be the best tool to use if I run it that often. Is there another better tool that I can use or install on Ubuntu 11.04 that will be a better option? Is there a way to fix the above cron?