Kafka Tiered Storage: Setup, Monitoring, and Cost Savings
Broker EBS is expensive, and 90% of Kafka data is cold. Tiered storage offloads old segments to object storage — done right, it cuts infra bills by more than half while keeping historical replay a single fetch away.
Why Tiered Storage Now
KIP-405 landed in preview back in Kafka 3.6 and is fully production-ready in 4.x. Tiered storage lets brokers keep only a hot window on local disk and delegate everything older to S3, GCS, or Azure Blob. The savings compound at scale — a 200 TB cluster typically costs 60–80% less to run.
Smaller Brokers
Local disks size for hot data only. Broker footprint shrinks and rebalances get dramatically faster.
Object Storage Pricing
S3 is roughly 10x cheaper per GB than EBS gp3. For long retention, that difference dwarfs everything else.
Infinite Retention
Weeks of retention become months without buying new brokers. Compliance replay stops being a capacity conversation.
Enabling Tiered Storage
Broker Configuration
Topic Configuration
Metrics That Only Exist with Tiered Storage
RemoteCopyBytesPerSec
Rate at which segments upload to object storage. Sudden drops signal a stuck uploader or IAM regression.
RemoteFetchLatencyAvg
Time to serve a historical read from tiered storage. Alert on p95 above the SLO for compliance replay.
RemoteLogSizeBytes
Total bytes in remote tier per topic-partition. Feeds your object-storage bill forecast.
RemoteCopyLagBytes
Local segments waiting for upload. Sustained lag means local disks will fill even though remote is enabled.
Operational Patterns That Actually Work
Right-Size Local Retention
Match local.retention.ms to consumer lag p99 plus a safety buffer. Too short and every restart hits object storage.
Pre-Warm After Failover
A newly-leader broker has no local hot data. Trigger a background prefetch so first-consumer reads do not stampede S3.
Budget Object-Storage Request Cost
S3 GETs add up. Coalesce fetches with larger segments (512 MB+) and monitor request rate alongside byte volume.
Correlate with Cost Data
Link RemoteLogSizeBytes to your cloud bill through cost optimization dashboards so retention decisions have a dollar sign.
Common Failure Modes
Turn Tiered Storage Into Real Savings
KLogic surfaces upload lag, remote-fetch latency, and per-topic remote size so you can adopt tiered storage without operational blind spots.