Scenario: Planetwide Computer

The scenario of a planetwide computer is the planet equivalent to a matrioshka brain (star brain). Planetwide supercomputers can have hard drives bigger than whole cities and have the computing power of a trillion humans. Planetwide computers have the potential to hold thousands to billions of yottabytes of information, or quadrillions to sextillions of TBs. Computers this size can have the computing power of thousands to billions of yottaflops (septillion ops/second). From space, these look similar to ecumenopolises because the structure encompasses a whole planet. The megacomputer can communicate with moonwide computers if moons are present, or also any nearby satellite.

Part One: The Planet and its Moons
The planetwide computer would need satellites and/or moons for this. Make the moons moonwide computers, and then the satellites into big computers. Doing this would require partial to complete strip-mining of a nearby planet with lots of metals.

Part Two: The Star and its Planets
The systemwide computer will require you to make a Matrioshka brain around the star(s) in the system. The planets and moons in the system (gas giants not included) will need to have Part One repeated with them, and then large enough asterids also transformed. The original planet should be the central. Systemwide computers have the potential to store a septillion (10^24) terabytes.

Part Three: Local Stars
The nearby stars will also need to have parts one and two repeated for them. Throw Matrioshka brains around them, and a fleet of A.I. spaceships between star systems to travel faster than light. These computers have the potential to store over 20 septillion TB. Civilizations who build these should already be type K3, controlling a galaxy.

Part Four: Galaxy
Now for the whole galaxy. A black hole bomb would be placed at the center, extracting light energy from it. Hawking radiation would also be regionable. Computers of this scale have the potential to last a quattordecillion years (for the Milky Way, for instance) The black hole computer alone could hold the storage capacity of a Part Three computer. Place Matrioska brains on all of the stars and transform all large enough asteroids, rocky planets, and rocky moons into computers as stated in parts one and two. Place A.I. spaceships to travel between stars. These galactic-scale computers have a nonillion TB potential (nonillion with an N, or 10^30).

Part Five: Galactic Cluster
The nearby galaxies will also need parts three and four repeated for them. Throw black hole bombs on all of the galaxies nearby, and have a fleet of A.I. spaceships going through hyperspace or warp drive down wormholes. These computers have the potential for storing hundreds of nonillions or decillions of TB data. Civilizations who build these should already be K3.5+, controlling many galaxies.

Part Six: Universe
Now for a universe. Place black hole brains and Matrioshka brains on all of the stars and black holes. Place a bigger black hole bomb around the Great Attractor. These computers have the potential for storing an undecillion to a quattordecillion TB data at a universe scale about 93 billion light-years diameter.

Scale of Data

 * Coin: 1 Bit
 * Letter (ASCII): 1 B
 * Ukulele chord: 18.8 B
 * Batch File: 500 B
 * Large Batch: 1.5 kB
 * First Hard Drive (car sized): 5 MB
 * 2005 Flash: 100 MB
 * 2010 HDD: 100 GB
 * Modern hard drive: 2 TB
 * Human brain: 2.5 PB
 * Internet: 1.2 EB
 * Statewide computer: 1 YB
 * Low end planetary computer: 1000 YB
 * Hypothetical Pluto computer: 70000 YB
 * Hypothetical Proxima computer: 6000000 YB
 * Part 2 computer: 1000000000000 YB
 * Part 3 computer: 20000000000000 YB
 * Galactic computer (part 4): 1000000000000000000 YB

Giga-PCs and Humans
Humans will probably hit Kardashev 2 in a thousand years. Pluto could potentially be a candidate for planetary computer, together with Charon. This is some serious sci-fi here. With current technology, the chypothetical computer on Pluto, assuming that our giga-PC has similar components to desktop computers, the computer could hold close to fifty thousand yottabytes data. Add Charon's hypothetical twenty thousand yottabytes and you have 70000 YB (70000000000000000 TB or seventy octillion (70000000000000000000000000000) bytes data). Adding artificial satellites in orbit around Pluto away from its other two asteroid moons, Nix and Hydra, would stack the capacity higher. An ISS-sized hard drive could hold exabytes of data. Signals between Pluto and Charon have a 65.5 millisecond delay. The danger with this is that Charon's gravity could potentially rip the computer apart and that asteroids from nearby Kuiper Belt will impact.

Distant Future
In the distant future of a spacefaring humanity probably another 500 years from the Pluto computer, the human race will probably control Wolf 1061, Wolf 359, TRAPPIST-1, and the Alpha Centauri Triple System. Proxima Centauri and its planet Proxima b will make good candidates (if no aliens are present). If there are no aliens, build a PC. If there are, don't. A Proxima b computer would have an estimated one million yottabytes storage, plus a Matrioshka around the star. The Matrioshka would probably have millions of yottabytes storage. Total, you probably have about 6000000 YB (600000000000000000 TB or 6000000000000000000000000000000 bytes) storage. That would probably take decades to build.