Using the 12.7 series Intel RST OROM and drivers, windows 8.1 does not see the SSD array as SSD's, they are seen as HDD's. The Optimize tool does not Optimize, it actually defrags the array.

Also for the secondary Sata 3 controller, SSD's identified as HDD's.  

I can't figure out why this changed from 8 to 8.1, makes no sense.  Lets hope the problem is corrected in the RTM and that Microsoft doesn't forget about all the enthusiast who run RAID. 

Hi,

Does the issue occur during Windows 8.1 installation or after this?

Would you please let us know more details about the RAID array, is it software based or hardware based? I think this may be related to the driver software, please reinstall or update it to see if it works.

Thanks.

I would guess that the 8.1 preview does not have all of the drivers "in the box". It's a Preview.

Did you in-place upgrade or clean install from an ISO?

Do you have a uefi enabled BIOS\hardware?

.Net may be missing from the Preview also.

Create a bootable recovery media usb, boot to it and add the RST driver.

Definitely needed to add the drivers during a clean install.

Visit Intel and run the Driver Update Utility. Chipset drivers may be missing.

If you don't have an ICH10 controller, there could be migration issues. (Intel support)

.Net 3.0 or higher is needed for the storage controller management panel.

Tells us a little more about your setup or if you have resolved the issue.