http://wiki.centos.org/HowTos/SoftwareRAIDonCentOS5
has:
dd if=/dev/zero of=/dev/sda bs=512 count=64 dd if=/dev/zero of=/dev/sdb bs=512 count=64
Will the joker who put in this particular gem without any warnings or a clear explanation for those who need a clueby4 with regards to file systems please either remove the instructions or add a very clear warning that damage to file systems that is not recoverable will result if run on the wrong disk(s).
My successor at my previous job has gleefully followed those instructions (he seriously needs a clueby4 which is why he bothers to actually read HowTos) and on a production box (who wants pop-corn and soda? Sorry, the er support conversation will not be on irc) and I think this seriously highlights the need for HowTo writers to seriously consider their audience as dumb monkeys that just follow whatever you tell them to do without thinking if you do not list out things they first have to think about or questions they first need to answer.
Christopher