Hi team, i triggered server rebalance in my pinot cluster with 3 servers, but the segment reassignment shows the target server for all the segments as only one server. How can i make it assign the data to all 3 servers.

Yes, you need to increase the number of partitions

Yeah 150 TB of data on a single partition is certainly not recommended. But if repartitioning upstream isn't possible, on the Pinot side you could configure instance assignment for

COMPLETED

segments separately (see https://docs.pinot.apache.org/operators/operating-pinot/instance-assignment for more details).

CONSUMING

segments will always be assigned to a single server per partition (and per replica).

this one partition is for the testing cluster, for prod we will have more than 100 partitions.