SETUP: Wrote paragraph how to convert world databases into interleaved format.

SETUP.md

@@ -14,7 +14,24 @@ Setting up MTSatellite takes six steps:
 6. [Start the Minetest server](#markdown-header-start-the-minetest-server)
 
 ## Convert world database into interleaved format
-**TODO: Write me!**
+
+MTSatellite operates best if the block data of the world is stored in a LevelDB database with
+a key scheme called interleaved. With this key scheme you can pick up sets of neighbored blocks a
+lot quicker than with a plain database.
+See [Z-order curve](http://en.wikipedia.org/wiki/Z-order_curve) at Wikipedia for grasping the core ideas.
+MTSatellite can run on plain LevelDB or SQlite3 world databases but this reduces the performance significantly.
+This is also not tested very well and will likely break your database. So do not use it! Stay with the
+interleaved format!
+
+To convert your original plain SQLite3 or LevelDB database (Redis is not supported atm) to the interleaved
+LevelDB format you have to use `mtdbconverter`:
+
+    mtdbconverter -source-backend=sqlite /path/to/your/world/map.sqlite /path/to/your/world/map.db
+
+Depending on the size of your world and the speed this conversion will take some time.
+Change `-source-backend=sqlite` to `-source-backend=leveldb` if your world is stored as a LevelDB.
+`mtdbconverter` can also be used to convert your world back to the plain key scheme.
+See `mtdbconverter --help` for all options.
 
 ## Configure the Minetest server
 **TODO: Write me!**