Installing Ubuntu 13.04 on a MSATA SSD

Swap should be on hard drive. With 12GB of RAM you may never use swap. The only time you might use swap would be if you hibernate, but if booting from SSD hibernation does not save much if anything. I still suggest a little swap just to have some or maybe 2GB. Others have had no swap with that much RAM and said it works.

You need to change to AHCI and removed RAID meta-data on drives. That is probably why grub will not install as it sees the RAID and wants to install to RAID.

sudo dmraid -E -r /dev/sda
sudo dmraid -E -r /dev/sdb

Is system UEFI or BIOS? That makes a difference on where to install grub. If BIOS you install grub to the MBR of either drive, but preferred to install to SSD. If UEFI you install to efi partition.

If you use manual install and have already created partitions with gparted, you just need to select partition for / (root), choose format and what format (ext4 usually), likewise for /home but if /home already exists with data you DO NOT format. If swap already exists it will find it automatically.

I have a 28GB /(root) partition and use about 9GB including /home which has .wine with Picasa. I have lots of programs installed. I think you can installs games to /home so those would be on HDD. You can split system folders and add to HDD like you do with /home but that should not be required.

All system folders in / can be partitions. Usually only done for servers with specific requirements.

Explanation of file structure

http://www.tuxfiles.org/linuxhelp/linuxdir.html

http://www.pathname.com/fhs/pub/fhs-2.3.html

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

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

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