I have quick questions about two properties:
For cluster.routing.allocation.cluster_concurrent_rebalance, I see in the documentation I see that the default is 2. Looking at source code I see that for unlimited is "-1". My question is: what does increasing the setting by 1 mean in terms of rebalance performance? To get "significantly faster" than 2, do you have to move it to something like 4 or 10 (or 20?).
For low/high watermarks, in the [documentation] (https://www.elastic.co/guide/en/elasticsearch/reference/current/disk-allocator.html) I see the default for low is 85% and high is 90%. If we want to set our low watermark to 95%, do you have any recommendations on what to set a high watermark? Setting it to either the same as the low watermark (95%) or the same range as defaults (+5% so 100%) both seem problematic.