I mean, nothing is really going to be as performant as Redis if you put it on disk.

The closest thing I can think of off the top of my head is MongoDB. Mongo will combine with on disk and in-memory storage. But you can do pretty much all the same things within mongo, just slower. It might not be that huge of a difference in performance depending on exactly what your doing of course. But if you're doing something in Redis that is, say, doing 100k+ ops/sec, you're highly unlikely to get that in mongo.