I am currently running Windows 10 and would like to install Ubuntu as it is much more convenient than Windows for coding Ruby On Rails. 

Though I am not sure how to do it properly.

My setup: 

* One 256GB SSD with Windows boot on it
* One 3 TB HD where I store files (music ...) and also some large Windows install (Steam and games mostly)

I thought I could dedicate a partition on the 3TB HD drive to Ubuntu so I created a partition of 500 GB on this drive.

**Now Ubuntu install** 

I wanted to install on the 500GB partition so i selected 
" something else" 

Then highlighted my 500 GB partition. but got error : "No root file system is defined" 

then I went back to install location menu and selected " install Ubuntu alongside Windows Boot Manager" and it offers to create the install on the 256 GB SSD drive and call it "Ubuntu /dev/sdb6 (ext4)"

**So my question** : is it necessary to install it on the SSD drive ? There is only 100GB free on this drive and the proposed Ubuntu partition is 61 GB. I am not sure there will be enough left for swap.. 

Is it not possible to use the 500 GB partition even if it's not fast access ? (I have 32 GO ram so it may be only slightly low at start)