Question-86: What is the difference between chunk cache and OS page cache seen by the operating system?

Answer: The cache on memory defined as chunk cache, which is seen as a user memory by the operating system and part of the Cassandra process running. But OS page cache is seen as buffer memory. 

The chunk cache uses mostly NIO direct memory, and store the chunks into NIO to byte buffer. 

Question-87: What time zone is used by the Cassandra the database what the write operation?

Answer: All the write in Cassandra database uses the UTC time zone, you should convert it to local time only when generated output required to be read by human otherwise it is not at all needed. 

Question-88: Sometimes in your database you have seen low traffic intervals, which causes the Timeout between the node connections or with nodes in another datacenter. what can be reason?

Answer: During the low traffic intervals, the firewall configured with an idle connection Timeout can close connection to local nodes or with the nodes in another datacenter. And this can be avoided by setting TCP keep alive Timeout value.

Question-89: What is CPU frequency scaling?

Answer: In a newer version of Linux System a new feature is introduced which is called CPU frequency scaling or CPU speed scanning. This feature allows a clock speed to be dynamically set, so that server can run at lower clock speed when the demand for load is low, and helps in reducing the consumption of power and generating the heat output. Which significantly impact the cooling cost at the datacenter.

Question-90: Why it is recommended to disable the CPU frequency scaling?

Answer: The intention of having the CPU clock scaling is to save the cooling cost. Unfortunately, this behavior has the detrimental effect on the Cassandra cluster and throughput can be kept at a lower rate.