creating large test datasets

Hi,
I want to create some large test datasets, what is a good way to do
this?
I don't want to use fixtures, because i don't want them to run during
the normal db:fixtures:load rake command.
Should i create a new rake command say, db:fixtures:big:load and create
a directory called big_fixtures and store my yml files in there?
Is there a better way?

maybe try this
http://railscasts.com/episodes/126-populating-a-database