It started with a tweet from a coworker asking if I can recommend reading for making a master/master MySQL server. There are plenty of caveats about writing to only one master at a time, and that master/master is not write scaling, but I think I tackled it pretty well in the MySQL Administrator’s Bible. It is not a very long topic, so I made a PDF of the relevant pages. High Performance MySQL also has a few pages that I would recommend reading, and the third edition has similar information as the Bible, although it goes into more detail about why you might use master/master replication and what might go wrong. Unfortunately I could not find a resource for the few pages of text from High Performance MySQL, and I am not sure if this person needs the whole book for just a few pages.