It sounds like you're conflating strong consistency with ACID transactions. The strong consistency guarantee with QUORUM writes with Cassandra is only if the write is acknowledged as successful. If you write something successfully, you'll be able to read it. When a write fails the end state is undefined.
The definition of strong consistency does not require a rollback, nor does it define the behavior of the system during a write failure. Strong consistency makes no assertions regarding atomicity (all or nothing) or isolation.
The definition of strong consistency does not require a rollback, nor does it define the behavior of the system during a write failure. Strong consistency makes no assertions regarding atomicity (all or nothing) or isolation.