Need some clarity regarding buying Committed Use Discounts & Reservation for Compute Engine

[gunjan_823]

Hi everyone,

I'm currently working on identifying discounts a customer can get after applying CUDs on Compute Engine but I'm extremely confused in knowing the difference between CUD & Reservation. Can someone please explain me the difference between them? 

[jedihomer]

My understanding when we went through this was this:

A CUD is a committed use, i.e. I am going to pay for 10 CPUs and 100GB of RAM for 3 years.  As a result I get those at a discount whether I use them or not.

Now, say I'm currently only have 2 VMs running and that's taking up 8 CPUs and 80 GB of RAM.  I can make a reservation for the rest of the resources, so that I can definitely create and use the resources later, because if I don't make a reservation and go to create a VM and there are no resources left then GCP won't create the VM, so you're still paying for 10 CPU and 100 GB but can't use it.

However when we wen't through this, we didn't create reservations as we aren't using things like GPU etc that can be limited.

That's how I interpreted what they were anyway, I could be wrong though...