The Einstein host stats have gone crazy, the uncompressed file is 3.6Gb and parsing them all has caused one of the database drives to fill completely. I'm cleaning it up now.
*EDIT* I misquoted here. It's not the Einstein hosts causing the issue. Some of average tables went crazy (not sure why yet) in one of the databases and got to 40Gb each, this is what filled the filesystems. I've switched off that part of the stats whilst I investigate - normally the filesystems are about 50% full, though they fluctuate upwards by about 10% as temp tables are created and deleted. Averages are just used to show the average countryrank and average teamrank. Been running fine for over a year so don;t know what caused them to go wrong yesterday. The daily rollover might be wrong occasionally today as the system flip flops between the two databases, but it will correct itself tonight.