The Megapulse (Mp) is a fictional, universal unit of data within the Shadowrun setting. It is intentionally vague, yet from references to storage of written material, audio/video, and other miscellaneous data...It can be roughly rounded to a little under a gigabyte of data.
This may not seem like much, and notably so. The matrix crash set this technology back a very long ways. The wake of the awakening, the wars, the full reshaping of the political landscape, and espionage about every corner have not helped much with it.