Windows 8.1 on a bootcamped latest retina MacBook Pro ( Thunderbolt 2 ports) .

Lacie Little Big disk SSD thunderbolt 2 formatted NTFS RAID 0

The disk will not mount in windows 8.1 

I have turned off fast Startup

The disk will mount on Bootcamped iMac 27 with Thunderbolt 1 ports

How can it be fixed?

Apple says its a Microsoft issue.

Hi Bretthitch,

I  noticed you have posted a case before :
https://social.technet.microsoft.com/Forums/windows/en-US/543fc5b7-408e-4dfc-bcb1-34eef9bd9a63/thunderbolt-drives-not-mounting?forum=w8itprohardware

Just as I pointed out before ,to make a device work correctly ,we need a compatible driver.
I have checked the system requirements of this device .It is only be compatible with Mac.Here is a link for reference.
https://www.lacie.com/dk/products/product.htm?id=10621

Since it is only supported by the Mac machine and we won`t get a compatible driver with Windows 8.1 .So it will not work in Windows 8.1 .

NOTE: This response contains a reference to a third party World Wide Web site. Microsoft is providing this information as a convenience to you. Microsoft does not control these sites and has not tested any software or information found on these sites.

Best regards