Is it possible to buy another 250gb SSD (I already have 1 as my cache) and add it to the existing 250GB, creating 500GB total space?

 

 

Yes, you'll need to change the profile from the default raid1 to raid0 (or single):

 

 

Thanks johnnie, 

 

I watched this video and it explained everything. 

 

Link here for anyone else who digs up this post.