Running out of disk space is something which, of course, should never happen as we all setup monitoring and alerting and only run well behaved applications. But when it does happen we want things to fail gracefully. So what happens when mysqld runs out of disk space? The answer is: It depends It might start to wait until disk space becomes available. It might crash intentionally after a 'long semaphore wait' It might return an error to the client (e.g. 'table full') It might skip writing to the binlog (see binlog_error_action ) What actually happens might depend on the filesystem and OS. Fixing the disk space issue can be done by adding more space or cleaning up some space. The later can often be done without help of the administrator of the system. So I wanted to change the behaviour so that it MySQL wouldn't crash or stop to respond to read queries. And to also make it possible for a user of the system to cleanup data to get back to a normal state. ...