Felix is right.
Voldemort works in the following way. Given a key, it maps it to a partition (Virtual). The partition, is hosted by multiple nodes ( number of replica specified in the store definition).
So given a key, voldemort identifies the nodes to distribute this key to . Then it waits for the write required ( writes-required number specified in the store definition) to respond back successfully before returning success to the client.
When client reads inconsistent values ( depending on reads-required), client fixes the value on the server.
So if you emphasis on consistent data, you should run the store atleast in
3 replication factor , 2 writes and 2 read required.
Depending on the consistency, you can tune it to 2 preferred reads for optimizing the performance.