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



Question-: In your node Cassandra cluster, one of the node is down and the node is seed node. What is the next step (assuming you have nodes designated as seed node)?
A. You should quickly add replacement for this node.
B. You don’t have to worry as there two other nodes are available as seed node.
C. You should update the seed node info on each node in the Cassandra cluster.
D. Use the “nodetool removenode� command to remove that dead node, which will take care of updating seed info on each node.

Answer: C

Explanation: When seed node become the offline in the Cassandra cluster then you have to manually update the seed info on each node of the cluster.



Question-: You have node Cassandra cluster which is physically separated in two datacenters. nodes in each datacenter. You have found that one of the nodes is down in the Cluster (this is not a seed node). You need to replace this node from the cluster. What all are true, for replacing the node, rather than first remove and then add?
A. You don’t have to move the data two time
B. Same tokens will be used by the new replaced node.
C. Existing node will work as a backup new node.
D. Cassandra cluster would be offline for few seconds only

Answer: A,B,C

Explanation: When you replace the dead node in the cluster then you should not follow the strategy like first remove the dead node from the cluster and then add a new node to the cluster. Rather you should use the replace node strategy where you would keep the dead node as part of the cluster until the new node is added. And use the replace strategy by providing the option in jvm.option file. Which has various advantages like
A. You don’t have to move the data two time
B. Same tokens will be used by the new replaced node.
C. Existing node will work as a backup new node.
However, keep in mind, when you replace a node. It does not make Cassandra cluster offline.



Question-: While replacing a dead node in the cluster you have to update the jvm.option file with the “replace_address� properties on the new node, what value it should have?
A. IP address of the seed nodes
B. IP address of the new node
C. IP address of the existing dead node
D. List of IP address for all the seed nodes

Answer: C

Explanation: This question is easy to answer, you are replacing the dead node from the cluster. And this property needs be set on the new node. Hence, you have to provide the IP address of the node which you want to replace with this new node. Before replacing new node can copy the data from the dead node like save_caches, commitlog , token ranges etc.


Related Questions

Question-: In the latest version of Cassandra you can repair the data using NodeSync utility/service, which runs in background. Which of the below correctly applies for NodeSync utility?
A. Using nodetool you can start/stop/enable the NodeSync service
B. NodeSync can be enabled either only for all table or not at all.
C. NodeSync works on the segments which are specific to a table. Created by dividing tokens in equal size.
D. NodeSync prioritize the segment in order to meet the per-table deadline target.


Question-: NodeSync utility is used for repairing the data on each table level, which is further divided in the segments. Which of the following is a valid statement in this case?
A. While repairing a particular segment maintained as locked in nodesync_status table.
B. NodeSync depends on read repair path.
C. If across the datacenter if WAN (Wide Area Network) is not good. Then also NodeSync utility performance would not be affected.
D. NodeSync validates the data only if replication factor 2 or more.


Question-: When NodeSync utility needs to repair the data in a particular segment, it follows the read path. Please arrange the below in the read repair order flow.

A. Read data from all replicas
B. Pick the data with the latest timestamp
C. Repair node with stale data


Question-: Match the following configuration parameters and their usage.

A. gc_grace_seconds
B. max_hint_window_ms
C. deadline_target_sec
D. rate_in_kb

1. Defines the time Cassandra keeps tombstone around.
2. Once this expires nodes stop saving hints.
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4. Maximum number of bytes per second used to validate the data.



Question-: While reading the data Cassandra introduced a data structure named bloom filter. Which of the following correctly applies for using bloom filter?
A. It helps to find that data definitely does not exist or exists in an SSTable.
B. It helps to find that data probably does not exist in an SSTable or definitely exists in SSTable.
C. It helps to find that data definitely does not exist in an SSTable or probably exists in SSTable.
D. Increasing the bloom filter (by reducing the property value property bloom_filter_fp_chance) will require more memory.
E. In rarely read database, it is better to set bloom_filter_fp_chance to a much higher number.


Question-: You can change the bloom_filter_fp_chance using the Alter table statement and that would be applied immediately on existing as well as new SSTable?
A. True
B. False