How to calculate number of reads/writes going on in cassandra

Question

We want to calculate how many records are written/read to our cassandra cluster on per sec or day basis without Opscenter.

Answer 1

Opscenter is just reading the standard JMX presented by C* so you could do the same thing. The mbeans you are most likely interested in are

org.apache.cassandra.metrics:type=ClientRequest,scope=Read,name=Latency : Count
org.apache.cassandra.metrics:type=ClientRequest,scope=Write,name=Latency : Count

Grab these from all the nodes and you have your read and write counts.