> > If you use N=3, W=3, R=1 in Cassandra, you > should get similar behavior > > to HBase/HDFS with respect to consistency > and availability > > My understanding is that R=1 does not guarantee that you won't see > different versions of the data in different reads, in some scenarios. There > was an excellent Quora answer in this regard, I don't remember it offhand, > perhaps you can find the link to it or someone can provide it to you. >
Since this is fairly off-topic at this point, I'll keep it short. The simple rule for Dynamo goes like this: if (R+W>N && W>=Quorum), then you're guaranteed a consistent result always. You get eventual consistency if W>=Quorum. If W<Quorum, then you can get inconsistent data that must be detected/fixed by readers (often using timestamps or similar techniques). Joe is right, enforcing (W=3, R=1, N=3) on a Dynamo system gives the same (provably identical?) behaviour as HBase, with respect to consistency. -- Tim Ellis Data Architect, Riot Games
