I’ve got a Mac Pro 5.1 with a Sonnet Tempo Pro Plus SSD card that has two Samsung 850 EVO drives on it. I’m really looking for support in High Sierra to be able to create a nice RAID 0 drive from them and make it the bootable system drive. It’s a weird omission so far. I’m guessing it relates to what Apple is doing with APFS. I was hoping the RAID 0 boot support might arrive when fusion drive APFS support arrived. I can be patient if I know it’s coming, but it would be very uncool to have bootable raid support not exist in High Sierra as it has in OS’s up till now. I’m not in the beta program and have no inside info on this, but any reassurance that bootable RAID support is coming would sure be nice.