My opinion: cache on top of cache is asking for trouble and I do not believe that it is worth even trying. I would purchase a regular HDD to use with Optane.
This message was posted on behalf of Intel Corporation
We have moved your thread to the Optane(TM) Support Community.
We would like to inform you that you can use the SSHD with your Optane(TM) Module. This drive is SATA based so you can accelerate it with Optane(TM).
For more information, you can check the Frequently Asked Questions for Intel® Optane™ Memory.
Thanks for the information