Look in the redis.conf file that you are using:
# It is also possible to remove all the previously configured save
# points by adding a save directive with a single empty string argument
# like in the following example:
#
# save ""
Stop redis-server, configure it as stated above, throw away the .rdb file, and start redis-server.
From now on, on every restart, redis-server will start with no data. Plus, no automatic snapshotting will happen at all.
Note: I presume here that you have not configured AOF. If that's the case, the solution is similar to the method mentioned above.
Hope this helps, TW