Our product is running on a Raspbery Pi collecting data from sensors. The sensor data is stored in a relational open source database (hsql db). In case a power failure happens, the hsql database file sometimes get corrupt.

Does anyone know whether free high-end database (such as postgresql, MySQL) or commercial relational databases such as Oracle, Sybase, MS SQL are able to survive a power failures? From what I know they write a journal with which the last state before the power failure can be restored. That's good. But my question is much simpler: Do these database have a problem that the database files can be corrupt after a power failure or do they always reliable startup again after power failure?

I'm asking this, because our customer wants our application to survive a power failure and I need to be able to say that if he wants this, this or that high-end database would be required (which probably would consume too much resources on a Pi).

Thanks for any constructive answers.
Regards, Oliver