Will need to know more about the number of requests, iostats etc. There is no reason for it to run slower.
I just deployed cassandra 0.7.4 as a 6-server cluster and tested its performance via YCSB.
The result seems confusing when compared to that of Cassandra0.6.6. Under a write heavy workload(i.e., write/read: 50%/50%), Cassandra0.7.4 obtains a really satisfactory latency. I mean both the read latency and write latency is much lower than those of Cassandra0.6.6.
However, under a read heavy workload(i.e., write/read:5%/95%), Cassandra0.7.4 performs far worse than Cassandra0.6.6 does.
Did I miss something?