Persisting your data onto a disk is one thing. Making sure your data still exists when that disk goes away is a whole different thing. We're talking backups!
As previously discussed, RDB files are point-in-time snapshots of the state of the Redis dataset. Since this is precisely what a backup is, an RDB file is the perfect way to take backup of your data, even when you're using AOF as your primary Redis persistence method.
The key thing that you really need to be sure of is that you've got enough disk space. I recommend ensuring an amount of space equal to the system's memory for RDB backups. This is in addition to the disk space you've allowed for your AOFs.
You'll also need to know how ...