You cannot partition an external disk, a RAID disk or an internal disk on which FileVault encryption is in progress

I'm trying to Boot Camp my Mac Pro (Late 2013, MacPro6,1).

You cannot partition an external disk, a RAID disk or an internal disk on which FileVault encryption is in progress.
Restart your computer using an internal disk that is not part of a RAID set or try it again after FileVault has completed.

Well, this is an internal SSD (an OWC Aura), and there's only one intentional partition; so I don't know why it's telling me this.

> diskutil list
/dev/disk0 (external, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *1.9 TB     disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:                  Apple_HFS Kate's HD               1.9 TB     disk0s2
   3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3

> diskutil corestorage info disk0
disk0 is not a CoreStorage disk

> diskutil info disk0
   Device Identifier:        disk0
   Device Node:              /dev/disk0
   Whole:                    Yes
   Part of Whole:            disk0
   Device / Media Name:      OWC Aura SSD

   Volume Name:              Not applicable (no file system)

   Mounted:                  Not applicable (no file system)

   File System:              None

   Content (IOContent):      GUID_partition_scheme
   OS Can Be Installed:      No
   Media Type:               Generic
   Protocol:                 PCI
   SMART Status:             Not Supported

   Total Size:               1.9 TB (1920080281600 Bytes) (exactly 3750156800 512-Byte-Units)
   Volume Free Space:        Not applicable (no file system)
   Device Block Size:        512 Bytes

   Read-Only Media:          No
   Read-Only Volume:         Not applicable (no file system)

   Device Location:          External
   Removable Media:          No

   Solid State:              No
   Virtual:                  No
   OS 9 Drivers:             No
   Low Level Format:         Not supported

> diskutil info disk0s2
   Device Identifier:        disk0s2
   Device Node:              /dev/disk0s2
   Whole:                    No
   Part of Whole:            disk0
   Device / Media Name:      Kate's New HD

   Volume Name:              Kate's HD

   Mounted:                  Yes
   Mount Point:              /

   File System Personality:  Journaled HFS+
   Type (Bundle):            hfs
   Name (User Visible):      Mac OS Extended (Journaled)
   Journal:                  Journal size 147456 KB at offset 0x37e2000
   Owners:                   Enabled

   Partition Type:           Apple_HFS
   OS Can Be Installed:      Yes
   Recovery Disk:            disk0s3
   Media Type:               Generic
   Protocol:                 PCI
   SMART Status:             Not Supported
   Volume UUID:              A22B65B2-1BAF-3561-B295-EF8343111867
   Disk / Partition UUID:    B85D962F-C97C-4C64-99AC-FD6C2F47F173

   Total Size:               1.9 TB (1919220523008 Bytes) (exactly 3748477584 512-Byte-Units)
   Volume Free Space:        710.0 GB (710019452928 Bytes) (exactly 1386756744 512-Byte-Units)
   Device Block Size:        512 Bytes
   Allocation Block Size:    4096 Bytes

   Read-Only Media:          No
   Read-Only Volume:         No

   Device Location:          External
   Removable Media:          No

   Solid State:              No

What steps can I take to install Windows on this volume? Preferably, I'd like to make Bootcamp “just work.”