DataStax Cassandra Developer Certification Certification Questions and Answer (Dumps and Practice Questions)

Question : Please map the bwlow.
A. Murmur3Partitioner
B. RandomPartitioner
C. ByteOrderedPartitioner

1. Provides fast hashing and good performance
2. Uniformly distributes data across the cluster based on MD5 hash values
3. Partitioner for ordered partitioning

1. A-3 B-2 C-1

2. A-2 B-1 C-3
3. A-1 B-3 C-2
4. A-1 B-2 C-3

Correct Answer : 4
Explanation: The main difference between the two partitioners is how each generates the token hash
values. The RandomPartitioner uses a cryptographic hash that takes longer
to generate than the Murmur3Partitioner. Cassandra doesn't really need a cryptographic hash, so using the
Murmur3Partitioner results in a 3-5 times improvement in performance.

Cassandra offers the following partitioner that can be set in the cassandra.yaml file.
Murmur3Partitioner (default): uniformly distributes data across the cluster based on MurmurHash hash values.
RandomPartitioner: uniformly distributes data across the cluster based on MD5 hash values.
ByteOrderedPartitioner: keeps an ordered distribution of data lexically by key bytes

Question : Both RandomPartitioner and MurmurPartitioner uses a cryptographic hash to generates the token hash values

1. True
2. False

Correct Answer : 2
Explanation: A partitioner determines how data is distributed across the nodes in the cluster
(including replicas). Basically, a partitioner is a function for deriving a token representing a row
from its partition key, typically by hashing. Each row of data is then distributed across the cluster by
the value of the token.

Both the Murmur3Partitioner and RandomPartitioner use tokens to help assign equal portions of data to
each node and evenly distribute data from all the tables throughout the ring or
other grouping, such as a keyspace. This is true even if the tables use different partition keys,
such as usernames or timestamps. Moreover, the read and write requests to the cluster
are also evenly distributed and load balancing is simplified because each part of the hash range receives an
equal number of rows on average. For more detailed information.

The main difference between the two partitioner is how each generates the token hash values.
The RandomPartitioner uses a cryptographic hash that takes longer to generate than
the Murmur3Partitioner. Cassandra doesn't really need a cryptographic hash, so using the Murmur3Partitioner
results in a 3-5 times improvement in performance.

Murmur3Partitioner?
The Murmur3Partitioner provides fast hashing and good performance.
The Murmur3Partitioner is the default partitioning strategy for new Cassandra clusters and the right choice
for new clusters in almost all cases.

RandomPartitioner?
The default partitioner prior to Cassandra 1.2.

ByteOrderedPartitioner?
Cassandra provides this partitioner for ordered partitioning. It is included for backwards compatibility.

Question : You are designing Cassandra cluster, and you have been asked to span cluster in Geneva,
Nevada and Hyderabad. Which of the following replication strategies you will use for this.

1. SimpleStrategy

2. NetworkTopologyStrategy

3. Murmur3Strategy

4. RandomStrategy

Correct Answer : 2
Explanation: SimpleStrategy : Use only for a single data center and one rack. SimpleStrategy places
the first replica on a node determined by the partitioner.
Additional replicas are placed on the next nodes clockwise in the ring without considering topology
(rack or data center location).

Use NetworkTopologyStrategy when you have (or plan to have) your cluster deployed across multiple data centers.
This strategy specify how many replicas you want in each data center.
NetworkTopologyStrategy places replicas in the same data center by walking the ring clockwise until reaching
the first node in another rack.
NetworkTopologyStrategy attempts to place replicas on distinct racks because nodes in the same rack
(or similar physical grouping) often fail at the same time due to power,
cooling, or network issues.

Related Questions

Question : When you need to add new node to Cassandra cluster, you have to bring down Cassandra cluster?

1. True
2. False

Question : When your driver uses TokenAwarePolicy

1. Co-ordinator cannot be avoided, each read and write go through co-ordinator node

2. Co-ordinator is not used, each read and write directly go to the specific node, which data belong to.

3. It eliminates a hop for your data

4. 1 and 3

5. 2 and 3

Question : Which of the policy rely on coordinator

1. RoundRobin

2. DCAwareRoundRobinPolicy

3. TokenAwarePolicy

4. 1 and 2
5. 1 and 3

Question : In your node Cassandra cluster you see, that most of data is going to particular node only and others are
sitting idle. This is known as...

1. vnode

2. Bad Partitioning

3. Hot Spot

4. Dump spot

Question : You see, your node Cassandra cluster has a evenly distributed token. But still there is a Hot spot problem, how
can it be solved?

1. By adding new node in the cluster.

2. re-arranging the token in cluster

3. with the help of virtual nodes

4. It cannot be solved

Question : What is true, with regards to vnode/virtual node

A. virtual nodes allow us to create individual smaller token ranges per node and it breaks up these ranges across the cluster
B. Before Cassandra 3.0, vnode have 256 ranges per node
C. past Cassandra 3.0, there are much more token ranges per node (more than 256)
D. past Cassandra 3.0, it's much less, and it's configurable by the user (less than 256)

1. A,B,C
2. B,C,D
3. A,C,D
4. A,B,D
5. A,B,C,D