A Kafka cluster takes 50 MB/s, keeps data for 7 days, and stores 3 replicas. How much disk does that need?

Answer

About 91 TB. In review, anything from 60.7 to 137 counts as right.

The worked estimate

50 MB/s × 86,400 s = 4,320,000 MB ≈ 4.32 TB a day. × 7 days ≈ 30.2 TB. × 3 replicas ≈ 91 TB, before compression and free-space headroom.

Numbers: Numbers to know.

Review this in your daily deck → All cards in Streaming