Cassandra atomic reads/writes within a single ColumnFamily

Question

Cassandra's front page http://incubator.apache.org/cassandra/ states that:

Cassandra guarantees reads and writes to be atomic within a single ColumnFamily.

What exactly does that mean?
It sounds like it means that batch_insert() and batch_mutate() of two different rows, in the same CF is atomic and if the operation on one of the rows fails, the whole operation fails. but it sounds too good to be true... Is this correct?

Answer 1

I have an answer from Jonathan Ellis, Cassandra maintainer:

It's correct, if understood correctly. We should probably just remove it since it's confusing as written.

What it means is, if a write for a given row is acked, eventually, all the data updated in that row will be available for reads. So no, it's not atomic at the batch_mutate level but at the list level.