We have a Column Family that is immutable (no updates after the first write). Suppose we use RF=2 and W=1. Do we still need R=2, so that R+W>RF? Or is it sufficient to have R=1? My guess is yes, R=1 is sufficient since if it reads a row, the row has to be correct: it can't get stale data. But can it get NO data? That is, with R=1 might cassandra look on one of the two nodes, find no data there, and prematurely give up? In other words, does R apply only to (possibly failed) read attempts or only to successful reads?