First time I tun single instance of Cassandra and my application on a system (16GB ram and 8 core), the time taken was 480sec.

When I added one more system ,(means this time I was running 2 instance of Cassandra in cluster) and running application from single client , I found time taken in increased to 1000sec.   And I also found that that data distribution was also very odd on both system (in one system data were about 2.5GB and another were 140MB).

Is any configuration require while running Cassandra in a cluster other than adding seeds ?

hanks & Regards,
abhinav