Thread:Project:Support desk/Media wiki takes large disk space

We develop a MediaWiki website that maintains data for the Norwegian historical population register. It uses MySQL. Currently the register contains about 3.5 million pages and it supposed to be several tens more. The problem that we recently encountered is that the whole system takes much more of the disk space than we expected. All pages should not require more than 3.5 G but the used space is now approximately 266 G. Is it any way to detect what actually consumes all this space? And what is the remedy?