Sure... just get the disks installed and everything where you want it then go to the Security & Privacy pane in System Preferences and turn on FileVault. That will encrypt the SSD. Once that is done, just right click on the HDD and select "Encrypt" and follow the prompts. Once the HDD is encrypted eject it then unplug and plug in again and you will be prompted for the encryption password.
I am not exactly following your "unplug and plug in" comment.
Since the HDD would be a secondary internal drive, couldn't you just reboot and accomplish the same thing?
In that window there is a checkbox to remember the password in Keychain. Check that box and enter the password. Now once you boot to the SSD the HDD will automatically be mounted.
Is it safe to use the keychain for storing really sensitive things like your encryption keys?
Seems like that could be hacked fairly easily.
You can data on the HDD with this setup, but you cannot keep the users folder there. You will need to keep that on the SSD, then you can keep individual data like Documents etc on the HDD if you like.
So a secondary internal HDD would be more like an external drive and not a place just for data inside your user account?
Why not put everything on the SSD? Prices have dropped enough to make it worthwhile to get the space you need. No problem running encryption on a SSD, why did you think that would be a problem? Almost all Macs now come with a SSD.
Well, I have these reservations...
1.) From what I know, a HDD is much more reliable than a SSD. After all, a SSD is just a big Flash drive, right? I have know lots of friends who have lost lots of photographs because their SD Flash cards in their cameras crashed.
2.) In my current I have a 1 TB HDD. Do they make SSD that big or bigger? I was hoping to have at least 1 TB on this new laptop and maybe even more?
3.) Is a SSD as secure as a HDD? I have a lot of sensitive things like my business and taxes on my current MBP, and I need a solution that will protect my data from ever super smart hackers and crooks.