CASSANDRA Installation and Configuration 3

Question 1

What is the recommended OS setting to change for Cassandra to avoid swap-related performance issues?

Accepted Answer

Set vm.swappiness=0 or 1

Answer

Set vm.swappiness=10

Answer

Disable transparent huge pages and set swappiness=60

Answer

Enable zswap with swappiness=100

Question 2

What does 'nodetool decommission' do?

Accepted Answer

Safely removes a node by streaming its data to other nodes before leaving the ring

Answer

Forces a node to restart

Answer

Deletes all data on a node immediately

Answer

Marks a node as down in gossip

Question 3

Which parameter controls the maximum heap size for the Cassandra JVM?

Accepted Answer

Both B and C (they are equivalent)

Answer

cassandra.yaml: heap_size

Answer

jvm.options or jvm-server.options: -Xmx

Answer

cassandra-env.sh: MAX_HEAP_SIZE

Question 4

What does the 'nodetool snapshot' command create?

Accepted Answer

A full backup by hard-linking current SSTable files into a snapshot directory

Answer

A dump of all keyspace schemas to a SQL file

Answer

A binary export of the CommitLog

Answer

An incremental backup delta file

Question 5

What is the purpose of 'incremental_backups' in Cassandra?

Accepted Answer

Copies each new SSTable to a backups/ subdirectory after it is flushed from MemTable

Answer

Automatically compacts SSTables on a schedule

Answer

Streams data to a remote backup cluster

Answer

Replicates CommitLog segments to S3

Question 6

In cassandra.yaml, what does 'concurrent_reads' control?

Accepted Answer

The number of threads dedicated to serving read requests

Answer

The number of client connections allowed

Answer

The maximum number of SSTables read simultaneously

Answer

The CQL read timeout in milliseconds