Comment 2 for bug 1605841

Cheng - reducing fraction replicas (3.5 => 3.0) is a *very* rare process compared to *increasing* the replica count (like when gradually adding a region) - I'm not even sure I understand the use-case?

Do you have any additional testing for increasing fractional replica counts - or does this issue only come up when reducing replica count?

As you know, there's always always more than one solution that would deliver the desired result, but some solutions might better align with existing assumptions and invariants in the ring builder code - so we need to make sure we first clearly state the problem.

Is the problem mainly an efficiency issue? How quickly (multiple rebalance; move too many parts?) the rebalance makes the reduced replica count change? Or is there a correctness issue as well (some invalid internal state that prevents the ring for ever fixing the balance issues)?