Windows 10: 1TB SSD won't back up to nearly empty 4TB HDD Part 2

The last time I tried to ask this question someone came back saying 365 isn't a backup solution; I know this. I'm trying to use the storage pool built into Windows 10. I have two 1TB SSD trying to run a mirror and two 4TB HDD intended to be the house Plex/File Server/Backup Location then mirrored. I'm trying to use the PC partially as a file server and backup location for the other PC's in the house. If you look at the F: drive you'll see I have nearly the full 4TB available on it. But when I attempt to move or copy anything to that drive it says it's full. I've added a bunch of scree

:)

 

Ugrading my 1TB MBR HDD to a 4TB GPT SSD

You should do steps as follows

1) clone 1TB hdd to SSD

2) run mbr2gpt utility to convert ssd to uefi

Convert Windows 10 from Legacy BIOS to UEFI without Data Loss

3) extend 1tb partition on SSD to 4TB using tool like Easeus Partition Master (free version is ok).

Step 2 is the critical step.

 

1TB SSD won't back up to nearly empty 4TB HDD

I have a PC that I built to double as my wife's work computer and a file/media server for the house. Her work is mainly web based so it's not very resource intensive. She said its been bogging down lately so I logged in to see what I could find. The giant red flag (for me) that I found is that it has never successfully run a local backup. OneDrive backups seem to be working fine.

The box has two 1TB SSD's and two 4TB HDD. I think I have it set up (via Storage Pool) to mirror one SSD to the other then backup to one of the HDD with the second HDD creating a backup there too. Long story short I thought I was being overly cautious but I'm now freaking out as it won't backup. When I try to manually create an image (to the second SSD) and a backup to the "Storage Space" HDD they both fail saying there isn't enough space. Unfortunately I'm stuck at work and can't provide better details. I hope my question makes sense.

How do I figure out home I'm "running out of space" in this setup? Both of the HDD's have less than 1TB used on either of them.

 

Ugrading my 1TB MBR HDD to a 4TB GPT SSD

Didn't work.
When I cloned the hdd to ssd, I could boot from the ssd.
When I ran the mbr2gpt tool (following a guide) after booting into the ssd, it says the conversion was successful but couldn't update reagent.xml. Disabling and enabling it didn't help. I didn't think it was a big deal.
Anyways when I changed to uefi, windows boot manager was #1 and Onboard NIC was #2 and #3, I ended up in windows repair and couldn't get out, so I just boot back to my hdd and here I am.