Interview Questions - Google - Design and describe a system/application that will most efficiently produce a report of ... ?

Design and describe a system/application that will most efficiently produce a report of the top 1 million Google search requests.These are the particulars. * You are given 12 servers to work with. They are all dual-processor machines with 4Gb of RAM, 4x400GB hard drives and networked together.(Basically, nothing more than high-end PC's) * The log data has already been cleaned for you. It consists of 100 Billion log lines, broken down into 12 320 GB files of 40-byte search terms per line. * You can use only custom written applications or available free open-source software.