Topology: VL822 hub + 4x ASM235CM (?) USB Gen2 - SATA bridges.
Tested with 4x WDC WD80EAZZ-00BKLB0 on an AMD X399 chipset.
~200MB/s from a single drive (this is about what the drive can do).
On a Gen1 port, I get ~400MB/s across all 4 drives. On a Gen2 port, ~800MB/s, give or take.
Power buttons power cycle the individual ASMedia controllers.