Recovery is done, system is up and running. MariaDB works fine again. As it didn't even react to a SIGKILL and completely blocked even a shutdown, we had to hard-reset ananke. Afterwards, MariaDB was running fine; tables are undergoing a consistency check. There's no indication of circumstances that could have led to this situation, so we suspect a rare bug in MariaDB itself. No other hosts were affected, and the underlying storage system is completely healthy with no errors.
