I work freelance so I do loads of interviews. I would estimate that about 90% of questions I'm asked relate to performance tuning and version upgrades. These are the things that people seem most afraid of so they tend to ask lots of questions. Depending on who's interviewing you questions about backup and recovery are popular. I suppose it depends on the type of work you are looking for.
Most of the time the interviewer knows far less than you so keep cool and look confident.