I recently upgraded my Windows 7 to Windows 8.1 with a new fresh installation.
The OS is running under a separate HDD 10k.
I also have a Raid 5, but now Windows 8.1 recognizes it as a mass storage and ask to format it because can find the file system.
The Raid 5 is configure under the BIOS and is functional. The controller is AMD SB950. The motherboard is Asus M5A97. I tried to install the chipset driver, but no difference.