Need a Cassandra Datacenter Quorum Read and Datacenter Quorum Write.
Add 1 new enum DC_Quorum. basically reads with this will not span across the datacenter it will use the existing nodes in the Datacenter which has this data and read from it.
For writes - All the data centers need to get this data, (datac enters will be configured in the storage-config.xml and number of replicas in it). Once configured write will basically write to all the nodes in all the datacenter but will wait only for the write in the current datacenter.
Example: We have 3 Datacenter A,B,C A has a replication factor of 3, B has 2 and C has 2. DC_Quorum write will make sure to write on 2 of 3 nodes in A.... B and C (total 4 +1) nodes will be eventually consistent.
Changes will be in RackAware, storage, read and write classes.