My pool Shrunk

Intel(R) Core™2 Quad CPU Q9400 @ 2.66GHz with 8GB Ram

4 Hard drives:

6Tb, 6TB, 4TB, 4TB

The two 6TB are mirrored
The two 4TB are mirrored

I know I’m a little low on Ram, but It has been running fine for months.
The problem is with the 4TB pool

Again it has been running ok, I started getting messages that I was at 74% and should stay below 80% for optimal performance. I said I had under 900GB of space left. I went in and deleted a good amount of files, more than 1TB. To my surprise, after I deleted those files I did not gain my space back. Instead, my pool is now 2.27TB. It used to be a little over 3TB. So essentially, my pool was shrunk by the amount of Data that I deleted. I tried doing searches and did not find anyone with this exact problem. Is this just a sign that my drives are dyng or is there something I can do or I’m missing. I thought of dumping and redoing the pool to see if I get my space back, but I’m not sure if that will work and wonder if there i an easier solution. I’m still fairly new to truenas, any help will be appreciated.

After further review:
Windows says 844GB free of 2.27TB
Linux (Ubuntu) says I have 906GB free of 2.5TB
Truenas Pool says 844 available out of 3.5TB

To add more weirdness to the mix:
I’m running Plex from this system. There where movies there I deleted. The movies still show. They won’t play and ask me to make sure the file is still there. When I scan the drive. The movies do not disappear. I don’t know if this is related to the main problem or a separate issue but I thought it could potentionally be a symptom.

Snapshots retain references to old data.

To recover the space you need to delete the old snapshots too

Why two pools?

Why not a pool with two mirrors?

Well, To be honest. I started this system with the two 4TB. When I got the two 6Tbs I saw I could do a mirror and add them. It caused problems. I thought it was a fluke, I tried again, problems. So I created the second pool and all was good after that.

So that’s what I need to do? Delete the snapshot? what about forcing it to do a new snapshot?

Snapshots ensure that the space used by all the data they reference can never be reused. While they exist.

If you list your snapshots you should be able to see how “big” they are, as you delete stuff that is still in the snapshot, the snapshot will appear to become larger.