This means that nodes in cassandra cluster contain data that has been sharded onto serveral nodes as well as this sharded data may be replicated further across several nodes ? So cassandra storage utilizes both sharded as well as replication for load balancing? Is this correct ?
On Mon, Jan 3, 2011 at 11:28 PM, Peter Schuller <peter.schul...@infidyne.com> wrote: >> What is the meaning of eventual consistency in Cassandra when nodes in >> a single cluster do not mantain the copies of same data but rather >> data is distributed among nodes. Since a single peice of data is >> recorded at a single place(node),Why wouldn't Cassandra return the >> recent value from that single place of record? How do multiple copies >> arise in this situation ? Where are the replicas in Cassandra cluster >> ? > > There is normally not just a single copy. If you run with RF > (replication factor) = 1, you have a single copy. But this is only > useful if you don't care about redundancy at all. > > With multiple replicas, the consistency depends on what you're doing. > For example the choice of consistency level (see the levels listed on > http://wiki.apache.org/cassandra/API). > > However note that even with RF=1, there are some things that are still > only "eventual". For example if you submit a batch mutation, > concurrent readers may see a partially applied batch mutation for a > given row even though it is only being written to a single node. > > -- > / Peter Schuller >
