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Apache Cassandra

Configuration

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This section covers the files that shape Cassandra startup, topology, and logging behavior. Read the landing page first, then open the file that matches the thing you want to change.

Read This First

File Use it when you need to…​

cassandra.yaml parameter names and units

Understand the cassandra.yaml renames and unit syntax before you change values.

JVM options

Set the static JVM flags for Cassandra nodes and client tools.

cassandra-env.sh

Compute JVM settings from the host at startup, such as heap sizing.

cassandra-rackdc.properties

Describe the local rack and datacenter for the snitch.

cassandra-topologies.properties

Define rack and datacenter mappings explicitly for PropertyFileSnitch.

logback.xml

Change log levels and log destinations.

Edit Order

If you are changing more than one file, use this order:

  1. cassandra.yaml value names and units

  2. JVM startup settings

  3. Rack and datacenter topology

  4. Logging configuration

That order keeps startup behavior, placement, and logging aligned.

What Changed in Cassandra 6

Cassandra 6 keeps the same configuration file set, but some files now carry new defaults and naming rules. In particular:

  • JVM settings now favor JDK 21 and Generational ZGC when you use the Cassandra 6 defaults.

  • Rack and datacenter settings matter more because TCM and the snitch use them to place replicas and reason about topology.

  • cassandra.yaml parameter names were normalized so unit suffixes are part of the value, not the field name.

If you only need the parameter-renaming reference, open the cassandra.yaml parameter names and units reference.