I am observing that my performance is drastically decreasing when my data size grows. I have a 3 node cluster with 64 GB of ram and my data size is around 400GB on all the nodes. I also see that when I re-start Cassandra the performance goes back to normal and then again starts decreasing after some time.
Some hunting landed me to this page http://wiki.apache.org/cassandra/LargeDataSetConsiderations
which talks about the large data sets and explains that it might be because I am going through multiple layers of OS cache, but does not tell me how to tune it.
So, my question is, are there any optimizations that I can do to handle these large datatasets ?