Ideally, yes. It's not actually the case though. Again, ideally. Well tested databases have evolved to have to survive arbitrary power cuts- even in the middle

Ideally, yes. It's not actually the case though. Again, ideally. Well tested databases have evolved to have to survive arbitrary power cuts- even in the middle of a transaction; and so have slowly become reliable enough to trust to start from on-disk state only. Good f-in' luck bringing your db flavor of the month back online from disk state alone. Hope you didn't have any transactions open to your DB before it got rescheduled to a different node in your cluster.