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

Setting vm.swappiness=1 (or 0) prevents the Linux kernel from swapping Cassandra's JVM heap to disk, which would cause severe latency spikes.

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

nodetool decommission moves the node's token ranges to other nodes and then cleanly removes it from the ring.

Question 3

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

Accepted Answer

Both B and C (they are equivalent)

Answer

Both -Xmx in jvm.options (newer installs) and MAX_HEAP_SIZE in cassandra-env.sh set the JVM max heap; which file is used depends on the Cassandra version.

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

nodetool snapshot creates a point-in-time backup by hard-linking the current SSTable files into a per-keyspace snapshot directory without copying data.

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

When incremental_backups is enabled, every newly flushed SSTable is hard-linked into a backups/ folder, enabling point-in-time restore between snapshots.

CASSANDRA - Apache Cassandra Database Practice Test

CASSANDRA - Apache Cassandra Database Practice Test

CASSANDRA Installation and Configuration 3