# Use JBOD with Self-Balancing in Confluent Platform Self-Balancing Clusters can balance data across the disks within a single broker in clusters that use Just a Bunch of Disks (JBOD) setups. With JBOD enabled, you run commands to move replicas between the disks on a broker so that data is evenly distributed. This intra-broker balancing is distinct from the inter-broker balancing that Self-Balancing performs automatically. Intra-broker balancing is on demand only: you run a command when you want to rebalance disks, and Self-Balancing doesn’t trigger it as part of its self-healing. For an overview of Self-Balancing, see [Manage Self-Balancing Kafka Clusters in Confluent Platform](index.md#sbc). ## Enable JBOD support To enable JBOD support, configure multiple log directories and set the Self-Balancing and JBOD properties on the brokers and controllers. ### Prerequisites A cluster with a JBOD setup must specify multiple log directories in the `log.dirs` configuration in each broker’s properties file, where each log directory is on a different disk. If the log directories are not on different disks, Self-Balancing JBOD support doesn’t work. The following code shows an example of multiple log directories in a broker’s properties file: ```properties log.dirs=/mnt/disk1/kafka-logs,/mnt/disk2/kafka-logs,/mnt/disk3/kafka-logs ``` The `log.dirs` configuration is not [dynamic](configuration-options.md#sbc-kafka-configs-command), meaning that you must restart the brokers after you change it. After you configure multiple log directories, enable Self-Balancing for JBOD as described in the next section. ### Configure Self-Balancing for JBOD To enable Self-Balancing to balance data across broker disks: 1. Enable Self-Balancing by setting [confluent.balancer.enable](configuration-options.md#sbc-config-enable) to `true` in the properties file for every broker and controller in the cluster: ```properties confluent.balancer.enable=true ``` 2. Enable [confluent.telemetry.metrics.collector.volume.include.logDirs.label](configuration-options.md#sbc-config-logdirs-label) for each broker so that brokers communicate per-disk capacity information to Self-Balancing: ```properties confluent.telemetry.metrics.collector.volume.include.logDirs.label=true ``` This configuration is not dynamic, so you must restart the brokers after you set it. 3. Enable [confluent.balancer.jbod.enable](configuration-options.md#sbc-config-jbod-enable) so that Self-Balancing balances data across disks. Set this in the properties file for every controller in the cluster: ```properties confluent.balancer.jbod.enable=true ``` This configuration is not dynamic, so you must restart the controllers after you set it. These configurations work together: Self-Balancing balances data across disks only when all are set. For the full requirement list, see [confluent.balancer.jbod.enable](configuration-options.md#sbc-config-jbod-enable). ## Disable JBOD support To disable JBOD support, set the JBOD configuration to `false` on the controllers and stop the brokers from emitting per-disk capacity metrics. Without JBOD support, Self-Balancing doesn’t work with multiple disks. Before you disable JBOD support, ensure that no intra-broker rebalance is in progress (see [Limitations](#sbc-jbod-limitations)). Complete the following steps: 1. Set [confluent.balancer.jbod.enable](configuration-options.md#sbc-config-jbod-enable) to `false` in the properties file for every controller in the cluster, and restart the controllers: ```properties confluent.balancer.jbod.enable=false ``` 2. To stop the brokers from emitting per-disk capacity metrics, set [confluent.telemetry.metrics.collector.volume.include.logDirs.label](configuration-options.md#sbc-config-logdirs-label) to `false` in the properties file for every broker, and restart the brokers: ```properties confluent.telemetry.metrics.collector.volume.include.logDirs.label=false ``` ## Balance data across disks Use the `kafka-rebalance-cluster` command-line tool to balance data across the disks on your brokers. To learn more about this tool, see [Monitoring the balancer with kafka-rebalance-cluster](configuration-options.md#sbc-kafka-rebalance-cluster). ### Preview an intra-broker rebalance Run the command with the `--intra-broker-rebalance-dry-run` flag to compute and review the rebalance plan without moving any data: ```bash kafka-rebalance-cluster --bootstrap-server --command-config --intra-broker-rebalance-dry-run ``` The output shows the proposed moves, the goals evaluated, and the projected cluster load before and after rebalancing. For example: ```text Computing intra-broker rebalance plan... Optimization has 53 intra-broker replica(2968.00 MB) moves with a cluster model of 12 recent windows and 100.00% of the partitions covered. New brokers: []. Dead or removed brokers: []. Violated goals before optimization: [IntraBrokerDiskCapacityGoal, IntraBrokerDiskUsageDistributionGoal]. Violated goals after optimization: [IntraBrokerDiskUsageDistributionGoal]. Goals which generated movements: [IntraBrokerDiskCapacityGoal, IntraBrokerDiskUsageDistributionGoal]. ... On-demand balancedness score before and after: 0.00 -> 62.26. ``` ### Run an intra-broker rebalance Run the tool with the `--intra-broker-rebalance` flag to start moving replicas between disks: ```bash kafka-rebalance-cluster --bootstrap-server --command-config --intra-broker-rebalance ``` ```text Triggering an intra-broker rebalance... Triggered an intra-broker rebalance operation. You can check its status by calling this command again with the `--describe` option. ``` Check the status of the rebalance with the `--describe` flag: ```bash kafka-rebalance-cluster --bootstrap-server --command-config --describe ``` ```text Uneven load balance status: HealUnevenLoadTrigger: ANY_UNEVEN_LOAD Current: BALANCING Last Update Time: 2026-05-04_09:02:08 UTC Previous: BALANCED Last Update Time: 2026-05-04_03:23:04 UTC ``` ## Limitations The following limitations apply to Self-Balancing JBOD support: - Intra-broker rebalance is on demand and is not triggered automatically as part of Self-Balancing self-healing. Monitor your intra-broker disk usage and use the [balancing commands](#sbc-jbod-balance-commands) to balance data across broker disks. - The balancing commands don’t work if Self-Balancing is running an existing reassignment. Wait for the reassignment to complete, and then run the intra-broker rebalance command. - Unlike with brokers, Self-Balancing doesn’t automatically detect a dead disk or take any action for one. The balancing commands don’t work when a dead disk is present. - Self-Balancing cannot expand or shrink the number of broker disks. ## Tune intra-broker balancing Use the following configurations to tune how Self-Balancing balances data across disks: - [confluent.balancer.intra.broker.throttle.bytes.per.second](configuration-options.md#sbc-config-intra-throttle) configures the replication throttle limit for intra-broker movements. - [confluent.balancer.num.concurrent.intra.broker.partition.movements.per.disk](configuration-options.md#sbc-config-intra-movements-per-disk) changes the parallelism limit on intra-broker movements. - [confluent.balancer.intra.broker.disk.max.load](configuration-options.md#sbc-config-intra-disk-max-load), [confluent.balancer.intra.broker.disk.balance.threshold](configuration-options.md#sbc-config-intra-disk-balance-threshold), and [confluent.balancer.intra.broker.disk.min.free.space.gb](configuration-options.md#sbc-config-intra-disk-min-free) control how Self-Balancing acts when an intra-broker rebalance runs. The following example sets these configurations to their default values in a broker properties file: ```properties confluent.balancer.intra.broker.throttle.bytes.per.second=10485760 confluent.balancer.num.concurrent.intra.broker.partition.movements.per.disk=1 confluent.balancer.intra.broker.disk.max.load=0.85 confluent.balancer.intra.broker.disk.balance.threshold=1.1 confluent.balancer.intra.broker.disk.min.free.space.gb=0 ``` The throttle is a [dynamic option](configuration-options.md#sbc-kafka-configs-command), so you can also adjust it while the cluster is running: ```bash kafka-configs --bootstrap-server --entity-type brokers --entity-default --alter --add-config confluent.balancer.intra.broker.throttle.bytes.per.second=20971520 ``` For full configuration details, see [Self-Balancing configuration](configuration-options.md#sbc-configs-on-brokers). ## Related content - [Manage Self-Balancing Kafka Clusters in Confluent Platform](index.md#sbc) - [Configuration Options and Commands](configuration-options.md#sbc-config-options) - [confluent.balancer.jbod.enable](configuration-options.md#sbc-config-jbod-enable) - [kafka-rebalance-cluster](configuration-options.md#sbc-kafka-rebalance-cluster) - [Auto Data Balancer](../rebalancer/quickstart.md#rebalancer)