Compare diskless and classic Apache Kafka® topics
Diskless topics are Apache Kafka®-compatible topics that store data in cloud object storage instead of broker-managed local disks.
Classic and diskless topics can coexist within the same Inkless Kafka service. In Inkless Kafka services, classic topics use managed remote storage by default and you cannot change this setting.
Compare classic and diskless topics
The table below highlights the key differences between classic Kafka topics and diskless topics.
| Feature | Classic topic | Diskless topic |
|---|---|---|
| Storage | Managed remote storage | Cloud object storage |
| Replication | Managed by Kafka brokers | Handled by the storage provider |
| Partition leadership | Required | Not required (leaderless data path) |
| Data path | Brokers write and serve data | Brokers batch data and write to object storage |
| Rebalancing | Required when scaling brokers | Not required |
| Segment format | Ordered files per partition | Objects tracked via metadata |
| Retention policies | Time- and size-based retention | Limited retention options |
| Compacted topics | Supported | Not supported |
| Transactions | Supported | Not supported |
| Topic creation | Auto-creation or manual | Manual or API-based only |
When to use classic or diskless topics
Use classic Kafka topics when:
- Your application requires transactions, compaction, or low-latency delivery.
- You need compatibility with tooling that depends on classic Kafka features.
- You rely on time- or size-based retention policies that are not yet available for diskless topics.
Use diskless topics when:
- High throughput and cost-efficient durable storage are required.
- Workload tolerates batching and slightly higher latency.
- Simplified broker operations and reduced infrastructure costs are priorities, especially for storage and cross-availability zone (AZ) traffic.
Use classic and diskless topics in the same cluster
Apache Kafka clients can produce to and consume from diskless topics using the same APIs as for classic topics. No client-side changes are needed.
A single Kafka cluster can contain both diskless and classic topics. This enables:
- Gradual adoption of diskless topics by migrating workloads incrementally
- Using classic topics for workloads that depend on unsupported features
- Consolidating streaming pipelines while optimizing for cost, durability, or throughput where needed