We ran 2.8 balancer with
HDFS-8818 on a 280-node and a 2,400-node cluster. In both cases, it would hang forever after two iterations. The two iterations were also moving things at a significantly lower rate. The hang itself is fixed by HDFS-11377, but the design limitation remains, so the balancer throughput ends up actually lower.
Instead of reverting
HDFS-8188 as originally suggested, I am making a small change to make it less error prone and more usable.