Help with Bloodmagic+ Disc/Clarity

Hello guys!

I'm currently following this build, i've never done a low-life before so i found it interesting

https://www.pathofexile.com/forum/view-thread/1963181/page/1

However, i cannot for the life of me find out how he's running discipline and clarity at once, not to mention he has arctic armour as well ( i understand he has a 30% mana res enchant). How do i run clarity/Discipline at once?

i went on PoE racing and most lowlife builders are doing this some taking reserve nodes and others arent. What am i missing!?

i assume you need the "reduced mana reserved" nodes from the skilltree