When would Cassandra not provide C, A, and P with W/R set to QUORUM? -

When both read and write sets on the quorum, I guarantee that the client is always updated during the reading The price will be found.

I know this may be a newbie question, but I do not understand how this setup does not provide consistency, availability and division.

With the quorum, you are unavailable (i.e. will not accept reading or writing) if available adequate replication Not available, you can choose to relax and read / write at lower stability level to provide availability, but then you will not be compatible.

There is also a case on which a quorum reads and writes that the latest "written" data has been retrieved, however, if a coordinator is not aware of the necessary division (i.e. gossip2 Since 3 nodes have not been declared after the failure), then it will write 3 replicas [assuming the quorum stability on the replication factor of 3] will write a living node, and the second 2 will not be (they are below). There is a time of writing time (this does not fail), even when writing a node is not a failure. Writing in "In progress" assume that the down nodes have come now if the customer further requests that data with quorum continuity be one of the two things:

1. Request two down nodes One goes, and the "Live" node client gets the latest data, reads the repair trigger, all is well.
2. The request goes to two nodes, the old data below was back (assuming has not been repaired). The coordinator is digested from the third, read the repair kicks inside. This occurs when the original writing is considered "complete" and later reads the latest data. All are good, but a customer will receive old data as if the writing was "in progress", but "not complete" is a very rare rare scenario where it will be. The noteworthy thing is that write to write Kasanda is fluctuating on the key, so it is generally ok to fix the problem properly to solve it, though, actually, the nodes are moving down, initial reading can be a problem. is. Usually you balance your stability and availability requirements. That is where the word comes tunable stability.