Aha,
RDB is NOT good if you need to minimize the chance of data loss in case Redis stops working (for example after a power outage). You can configure different save points where an RDB is produced (for instance after at least five minutes and 100 writes against the data set, but you can have multiple save points). However you'll usually create an RDB snapshot every five minutes or more, so in case of Redis stopping working without a correct shutdown for any reason you should be prepared to lose the latest minutes of data.
Hát aki adatbázisnak használja, annak egészségére.
A másik, meg hogy akkor is in-memory database, szóval az egész ott lesz a RAM-ban. Nagy adattömegnél ez nem járható.