apache/cassandra · warning

32bit JVM detected. It is recommended to run Cassandra on a

Error message

32bit JVM detected.  It is recommended to run Cassandra on a 64bit JVM for better performance.

What it means

At startup, Cassandra's checkJVMArchitecture startup check warns when the JVM does not have a large address space, i.e. a 32-bit JVM is running. Cassandra relies on memory-mapped SSTables (mmap), which a 32-bit address space severely limits, so 64-bit is strongly recommended. This is a logged warning, not a thrown exception; startup continues.

Source

Thrown at src/java/org/apache/cassandra/service/StartupChecks.java:599

        }
    };

    public static final StartupCheck inspectJvmOptions = new StartupCheck()
    {
        @Override
        public String name()
        {
            return "jvm_options";
        }

        @Override
        public void execute(StartupChecksConfiguration configuration)
        {
            if (configuration.isDisabled(name()))
                return;
            // log warnings for different kinds of sub-optimal JVMs.  tldr use 64-bit Oracle >= 1.6u32
            if (!DatabaseDescriptor.hasLargeAddressSpace())
                logger.warn("32bit JVM detected.  It is recommended to run Cassandra on a 64bit JVM for better performance.");

            String javaVmName = JAVA_VM_NAME.getString();
            if (!(javaVmName.contains("HotSpot") || javaVmName.contains("OpenJDK")))
            {
                logger.warn("Non-Oracle JVM detected.  Some features, such as immediate unmap of compacted SSTables, may not work as intended");
            }
            else
            {
                checkOutOfMemoryHandling();
            }
        }

        /**
         * Checks that the JVM is configured to handle OutOfMemoryError
         */
        private void checkOutOfMemoryHandling()
        {
            if (JavaUtils.supportExitOnOutOfMemory(JAVA_VERSION.getString()))

View on GitHub (pinned to 88fd0f6a0e)

Solutions

1. Install and run a 64-bit JVM (verify with `java -version` showing 64-Bit Server VM).
2. Reinstall the OS/JRE as amd64/x86_64 if the OS itself is 32-bit.
3. Set JAVA_HOME to the 64-bit JDK used by the Cassandra startup scripts.
4. Acknowledge and ignore the warning only for throwaway/test environments.

Example fix

// before (32-bit JVM)
java version "1.8.0_392" Java HotSpot(TM) Client VM
// after
java version "1.8.0_392" Java HotSpot(TM) 64-Bit Server VM

String arch = System.getProperty("os.arch");
String vmBits = System.getProperty("sun.arch.data.model", System.getProperty("com.ibm.vm.bitmode", ""));
if (!"64".equals(vmBits) || arch.contains("86") && !arch.contains("64")) {
    System.out.println("32-bit JVM detected; install a 64-bit JDK before starting Cassandra.");
}

When it happens

Trigger: Running Cassandra on a 32-bit JVM so that DatabaseDescriptor.hasLargeAddressSpace() returns false during the startup checks phase (StartupChecks.execute).

Common situations: Deploying on old 32-bit OS/JVM images, embedded or minimal containers built with 32-bit Java, or accidentally installing the i386 JRE on a 64-bit host.

Understand the failure class

Background: "unsupported platform" / "not supported on this platform" errors: what they mean and how to fix them — this error's family across 47 libraries.

Related errors

• <garbage collection summary>
• Non-Oracle JVM detected. Some features, such as immediate u
• The JVM is not configured to stop on OutOfMemoryError which
• The JVM is not configured to stop on OutOfMemoryError which
• Cassandra server running in degraded mode.

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/b7ebe512b17ed0a8. Report an issue: GitHub.