Fusion Drive

No. I think you have a misunderstanding of how Fusion Drive works.

It's not RAID, but Tiered Storage.

http://en.wikipedia.org/wiki/RAID

http://en.wikipedia.org/wiki/Automated_Tiered_Storage

You can use RAID and Tiered Storage together, but I have no idea if CoreStorage supports that on OS X.

You will get the capacity of your drives - 10% useable space for a single Logical Volume.

I believe it's worth it. I am running a DIY Fusion Drive on my 13" MBP (240GB SSD, 500GB HDD). From what you said, you are exactly the kind of user Apple thinks would benefit.

While you can install an SSD and HD in a Mac mini server, I doubt very seriously that they will function together as what Apple calls a Fusion Drive.

I take that back ...Google seems to think otherwise.

And, of course, Google knows all.....

I have the same configuration. I saw a post a couple of days ago that said that the support for fusion drive was built into O'S X and that ther was a way to turn it on in terminal. It seemed too complicated for me, but I'm hoping someone will come out wit an add on that will do it. I'm in no hurry, I don't use the 750gb drive now.

Found the link:

http://jollyjinx.tumblr.com/post/34638496292/fusion-drive-on-older-macs-yes-since-apple-has

It takes only 3 minutes and the instructions are here
http://www.mac-gamer.net/how-to/roll-your-own-fusion-drive/
I booted from an external drive

And here is the example
https://forums.macrumors.com/posts/16192143/

Blackmagic test for Fusion