Thanks for your question Ashwin,

If you’re targeting a partition size of 250 MB for 1 TB of data, the calculation gives you approximately 4,000 partitions:


Total Partitions= 1,000,000 /250 ~~ approx 4,000


Recommendation of 4,000-5,000 Partitions

1. Buffer for Performance: The recommendation of 4,000-5,000 partitions allows for a buffer. If you set it at exactly 4,000, you might not fully utilize available cores, especially in larger clusters.
2. Cluster Dynamics: More partitions can help with load balancing and prevent stragglers, particularly if data skew exists or if certain tasks take longer than others.
3. Future-Proofing: Setting the partition count slightly higher provides flexibility for varying data sizes or changes in the workload without needing constant adjustments.

Summary

The recommendation of 4,000-5,000 is to ensure you have enough partitions to leverage cluster resources effectively while also accommodating potential variations in data characteristics. Starting with around 4,000 is good, but having the capacity to scale up to 5,000 can be beneficial for performance tuning.

Hope this helps :)