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Datastax Cassandra Administrator Certification Questions and Answer (Pratice Questions and Dumps)



Question-: In Cassandra cluster when repairs are initiated?
A. While reading the data if it was found that data is not in sync then repair would be initiated.
B. You can manually initiate using the nodetool repair command.
C. Based on the property configure read_repair_chance it can randomly repair the node.
D. Once in 10 days repair would be done at least once.


Answer: A,B,C
Exp: There are various event for option through which nodetool repair can be initialized some of them are as below
• while reading the data if it was found that replica is not in sync with another node then repair would be initialized for that replica.
• if somebody manually initiate the command using the node tool.
• or if you are configuring the property read_repair_chance then based on that randomly the node would be repaired.



Question-: Which of the following parameter, would be used for defining the data validation for repair frequency with the NodeSync?
A. rate_in_kb
B. deadlinbe_target_sec
C. gc_grace_seconds
D. nodesync_repeat

Answer: B

Explanation: Table which has NodeSync enabled Has a property like deadlane_target_sec, Which is the time difference of the maximum time for validating the same data again. If this parameter is made in all parts of the that particular table are validated at least once or twice and data would be repaired.

Remember that this parameter that deadline_target_sec should always be less than GC Grace period (gc_grace_sec).



Question-: Which of the following parameters are related when configuring NodeSync to be completed in the given time frame?

A. deadline_target_sec
B. rate_in_kb
C. gc_grace_sec
D. rate_in_sync


Answer: A,B

Explanation: NoodeSync try to validate all the tables within their respective deadline, but it depends on what rate you have configured. Suppose you have 100 GB of a table size where you have configured deadline_target_sec=10 and rate_in_kb is set to 10 MB per second, then validation will not happen quickly and you may see following warnings in the system.log file.

• Rate in KB is too low to validate all the tables within their deadline.
• Rate in KB cannot be sustained by the node, if it is set very high

Remember NodeSync service is a per node service, hence parameter rate_in_kb is also set for node. Which defines maximum number of bytes per second used for validating your data for that particular table.


Related Questions

Question-: You are having node Cassandra cluster spanning two data centers. One of the seed nodes from this cluster is down and you have to replace that node. What all you would be doing?
A. You would update the Cassandra.yaml file for each node and remove the IP of dead node as seed node.
B. You would update the Cassandra.yaml file for each node and add the IP of new node as seed node.
C. You would be performing rolling restart on all nodes so that nodes are aware of the changes in the seed list
D. You would be updating the jvm.options file of new node and add the IP address of the dead node in replace_address property.


Question-: What all are the functionality of the seed nodes?
A. They would be contacted while bootstrapping to get the gossip info.
B. Any time any node can contact to seed node to get the gossip info from the seed node.
C. Seed node are always used when data read from the cluster.
D. They are also known as coordinator node


Question-: You want to replace the currently running node in the cluster for applying software patch on particular node, which of the following is correct for that?
A. You would first add a new node and then remove the old node on which the patch should be applied.
B. You would be replacing node by using replace_address property in the jvm.option file.
C. You must make sure that the consistency level One is used on the old node
D. You must make sure that the consistency level One is not used on the old node


Question-: You have created the Cassandra cluster using the “GossipPropertyFileSnitch�. This is a node cluster. Now you have found that the one of the node in the cluster is placed in the wrong rack. What would you do fix that?
A. Decommission node and re-add it to the correct rack and datacenter
B. Update the node’s topology and start the node.
C. Update the Cassandra.yaml file and restart the node
D. Bring down the cluster and then place the node in correct rack


Question-: You have your Cassandra cluster is setup in datacenters, and you want to remove one of the datacenters from the cluster. Which of the following steps at least you have to do to remove the Datacenter from the cluster?
A. No client should write on the nodes in the datacenter which is going to be removed.
B. We need to run the “nodetool repair –full�
C. Update the keyspace so that they no longer point to datacenter which is going to be removed.
D. Shutdown all the nodes from the datacenter which is being removed.
E. Run “nodetool assassinate� command on every node in the datacenter being removed.
F. Restart the all the nodes in remaining two datacenter


Question-: Which of the following statement is true with regards to the “nodetool drain� command?
A. It flushes all the SSTables to the disk
B. It flushes all the memtables to SSTables on disk.
C. It replays data from commit log
D. Cassandra will stops listening for connections from the client and other nodes.
E. You should use this command before upgrading a node to a newer version of Cassandra