I have a 4-drive RAID 0 for working data on my main home computer. Occasionally in the past, if the power went out or for no reason at all that I could tell, 2 of the disks would drop out and show up as "non-RAID" on the boot screen. Deleting the array, putting it back together with identical specs, and then recovering the partition using partition recovery tools would bring my data back. The disks are fine and have been forever except for dropping out like this occasionally.
Recently, things have escalated. These 2 disks now drop out every single time the machine boots after shutting down or hibernating. Sleep or restarts don't cause the problem, so basically I've stopped shutting the machine off for the last couple days.
After a ton of googling the only thing I could think was that the drives were spinning up too slowly or something and dropping out, so I setup a BIOS password to give them time. This hasn't helped.
I also re-seated all the SATA cables. No effect.
I'd like to keep this machine working. I'd certainly like it to hold on long enough to at least replace it with a quad-core Kaby Lake and Z270 machine if I have to replace it, but I don't think I can get work down on something this fragile for another month or two (or however long it's going to take Intel to get yet another incremental upgrade out). Even if I replace it, I'll probably want to re-purpose it as a fileserver or something useful.
The motherboard is an Asus P8Z68-M PRO. It's got an Nvidia 8800 GTS with the latest drivers that very occasionally bluescreens the machine since I installed Windows 10. Boot's from a RAID 0 of 2 SATA SSDs. Data's on the 4-drive RAID 0 of HDDs.
EDIT: PSU is a Hiper Type R MkII, 650W unit.