HBaseBackfillMerger does not seemingly make use of disabling autoflush. I can't see anything in site-xml suggesting it can be disabled by default so wonder if there is a design reason for this. We get a 10x increase in insert rate when auto flush is disabled and on a 6B record cube (Google tiles at 23 zooms for all species) this is crippling.

Before I propose a pull request, I thought I'd just ask.