Cassandra DataStream

HI i have an over night requirement, I need to Stream Data Continuously form one Cassandra Ring to Other Ring with out no Client Downtime,For example data stream from Cassandra Ring A to Cassandra Ring B where RIng A and RIng B are having different RF topologies this has to be done in next 24 hours, let me know if someone can help me in [login to view URL] reach back to me for this. I am considering to do this myself using SSTableLoader/splunk/hadoop integration as this is time sensitive i am reaching out for support,if there is any other way i am open for ideas,the ways i described above are fine or either way or any different way is fine too but job has to be done.