Configuring the buffered read size 

Configuring the buffered read size can reduce problems with wasted disk I/) and unnecessary garbage collection.

On read workloads, Cassandra 2.1 reads drastically more data than it emits over the network. This causes problems throughput the system by wasting disk I/O and causing unnecessary garbage collection (GC).

The location of the cassandra-env.sh file depends on the type of installation:
Package installations /etc/cassandra/cassandra-env.sh
Tarball installations install_location/conf/cassandra-env.sh

Procedure

  1. Open the cassandra-env.sh file for editing and scroll down to the JVM_OPTS.
  2. Set a value for the buffered read size. By default, the size is 65536.
    JVM_OPTS="$JVM_OPTS -Dcassandra.rar_buffer_size=65536"