This particular How-to, while it should be able to be utilized to set different drives for each part, is only starting how to set the "Home" or in this case the "Var" folder to a different drive from the system drive.
- Create a bootable USB for Vanilla OS (if you're attempting this in a virtual OS for Vanilla, then I am not sure how that works, try these steps and let me know how it works). If you're not sure how to create a bootable USB, you can look it up on Google as there are a plethora of ways. I prefer to use Balena Etcher though.
- Make sure your BIOS is set to boot using UEFI. (there is a guide in this forumn to help you determine the common BIOS setup for your brand of Motherboard, I'll link later)
- Boot into the USB
- Proceed to where you select your disks per normal.
- Select all the disks you wish to use. For this, we will only be using 2 drives: an SSD for the sytem and an HDD for the home/var.
- When you select multiple drives, you will have to choose "Manual partitioning" so click onit.
- The next window will have you select the following requirements out of the partitions already laid out in your drives: Boot, EFI, System/Root, Var (home), Swap (optional but necessary for hibernation, we will be skipping this one for now).
- Please note that this will clear your partitions for Boot, System and Var/home. As it is currently made, there is no avoiding this.
- Alright, select "Gparted" at the top. We need to make sure that your 2 drives have the correct partitions, sizes, and formats.
- Select the one for your system. We are going to assume that this is a 128 gb drive called SDA.
- Delete all the partitions here. (this will in the end clear ALL of your files, so back them up to another drive before proceeding)
- Create a 1024 MB partition set to EXT4, label it "boot" this is not required nor will it stick, but it is helpful to know what is what.
- Create another partition that is 512 MB set to FAT32 and label it "efi"