MCQs on Cassandra Performance Optimization | Cassandra

In this chapter, we delve into optimizing Cassandra’s performance by focusing on monitoring tools like Nodetool, managing the JVM and heap settings, understanding latency and throughput, and utilizing repair processes and tools. Additionally, we explore backup and recovery strategies to ensure data availability and performance in your Cassandra setup.

MCQs

Topic 1: Monitoring and Tuning with Nodetool

1. The primary function of nodetool is to:
   a) Backup data
   b) Monitor and manage Cassandra nodes
   c) Optimize SQL queries
   d) Deploy updates
2. Which nodetool command helps check the status of all nodes in a Cassandra cluster?
   a) status-ring
   b) status
   c) check-status
   d) node-info
3. What does the nodetool repair command do in Cassandra?
   a) Repairs the hardware of a node
   b) Synchronizes data between replicas
   c) Checks for missing data in the cluster
   d) Optimizes the JVM heap
4. nodetool can be used to:
   a) View the list of connected users
   b) Monitor disk space usage
   c) Edit cluster configurations
   d) Execute CQL queries
5. The nodetool flush command is used to:
   a) Clear the cache
   b) Flush memtables to disk
   c) Drop a table
   d) Rebuild the index
6. Which of these nodetool commands can help identify the current load on a node?
   a) info
   b) status
   c) tpstats
   d) describe-cluster
7. To check for potential data inconsistencies across nodes, you would use the nodetool command:
   a) cleanup
   b) repair
   c) decommission
   d) flush
8. Which nodetool command helps in managing the data for a specific keyspace?
   a) flush
   b) compact
   c) describe-keyspace
   d) cleanup

Topic 2: JVM and Heap Management

9. The JVM heap memory in Cassandra is responsible for:
   a) Storing read-only data
   b) Managing query executions
   c) Storing temporary data for processing
   d) Hosting external functions
10. What is the default heap size for Cassandra’s JVM?
    a) 512 MB
    b) 1 GB
    c) 2 GB
    d) 8 GB
11. Which JVM parameter is used to adjust the heap size in Cassandra?
    a) -Xms
    b) -Xmx
    c) -Xgc
    d) -Xmn
12. How does increasing the heap size in Cassandra affect its performance?
    a) Increases the chance of GC pauses
    b) Improves read throughput
    c) Reduces network latency
    d) Helps in faster data replication
13. Which of the following is the primary cause of long garbage collection (GC) pauses in Cassandra?
    a) Excessive heap memory usage
    b) Too many nodes in the cluster
    c) Network congestion
    d) Insufficient disk space
14. To minimize GC pauses, Cassandra recommends a heap size of:
    a) Less than 50% of available memory
    b) Greater than 75% of available memory
    c) Equal to the total memory
    d) Half the size of the disk space
15. What is the purpose of G1GC (Garbage First Garbage Collector) in Cassandra’s JVM?
    a) To increase throughput
    b) To reduce the frequency of full GC pauses
    c) To optimize replication
    d) To monitor node performance
16. Which of these JVM garbage collectors is considered best for Cassandra environments?
    a) CMS
    b) G1GC
    c) ParallelGC
    d) SerialGC
17. When tuning heap memory, what other factor must be considered alongside the heap size?
    a) JVM version
    b) Number of partitions
    c) Data locality
    d) I/O capacity

Topic 3: Understanding Latency and Throughput

18. Latency in Cassandra refers to:
    a) The rate at which data is processed
    b) The delay between a client’s request and the response
    c) The amount of data in the system
    d) The rate of data replication
19. What does throughput measure in a Cassandra cluster?
    a) Data storage capacity
    b) The number of queries per second
    c) Data consistency across nodes
    d) The time taken for a single query to complete
20. Which of the following actions will likely increase latency in Cassandra?
    a) Using a high replication factor
    b) Excessive disk I/O operations
    c) Lowering the number of partitions
    d) Using SSD storage
21. High latency in a Cassandra system can often be caused by:
    a) Efficient node communication
    b) Network congestion or slow disk I/O
    c) Low replication factor
    d) Optimized JVM settings
22. Throughput in Cassandra can be improved by:
    a) Reducing the number of nodes in the cluster
    b) Using fewer partitions
    c) Increasing the replication factor
    d) Optimizing query design and hardware
23. The consistency level in Cassandra affects:
    a) The reliability of the hardware
    b) The speed of query execution
    c) The number of replicas involved in a read or write operation
    d) The number of nodes in the cluster
24. What configuration setting is crucial for improving Cassandra’s write throughput?
    a) Read consistency level
    b) Write consistency level
    c) Compaction strategy
    d) Cache settings
25. Which type of compaction strategy helps improve write throughput in Cassandra?
    a) Leveled Compaction
    b) Size-Tiered Compaction
    c) Time-Based Compaction
    d) All of the above

Topic 4: Repair Processes and Tools

26. What is the main purpose of running the nodetool repair command?
    a) To check for corrupted nodes
    b) To update the schema
    c) To synchronize data across replicas
    d) To remove unused data
27. Repairing a Cassandra node helps prevent:
    a) Disk failures
    b) Data inconsistencies and stale reads
    c) Network latency
    d) JVM garbage collection issues
28. What is the most common tool used to perform repair operations in Cassandra?
    a) cqlsh
    b) nodetool
    c) cassandra-cli
    d) repair-tool
29. What is an issue that nodetool repair addresses during data synchronization?
    a) Disk corruption
    b) Replica mismatches
    c) Garbage collection pauses
    d) Node configuration errors
30. How often should repair operations be scheduled in Cassandra?
    a) Every few minutes
    b) Every 3-6 months
    c) Based on the consistency level and data write patterns
    d) Only when a node fails

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