SSD volume reporting too few free space (no snapshots)

[Zofoor]

Hi all!
I have a strange issue. I have a volume of one nvme ssd disk, 512 gb.

On the web interface I see those data:
- Used: 400.53 GiB
- Available: 48.97 GiB

Checking the used space, I get:
root@freenas:/mnt/nvme_volume # du -hs 79G .

I don't use snapshots in this volume (zfs list -H -t snapshot | grep nvme_volume reports 0 snapshots).

So, why does I lose almost 300 GiB of space? Any idea?

Code:

root@freenas:/mnt/nvme_volume # gpart list nvd0
Geom name: nvd0
modified: false
state: OK
fwheads: 255
fwsectors: 63
last: 976773127
first: 40
entries: 152
scheme: GPT
Providers:
1. Name: nvd0p1
   Mediasize: 500107776000 (466G)
   Sectorsize: 512
   Stripesize: 0
   Stripeoffset: 65536
   Mode: r1w1e2
   efimedia: HD(1,GPT,4d592c8e-761f-11e9-8f55-0cc47acb787c,0x80,0x3a385f88)
   rawuuid: 4d592c8e-761f-11e9-8f55-0cc47acb787c
   rawtype: 516e7cba-6ecf-11d6-8ff8-00022d09712b
   label: (null)
   length: 500107776000
   offset: 65536
   type: freebsd-zfs
   index: 1
   end: 976773127
   start: 128
Consumers:
1. Name: nvd0
   Mediasize: 500107862016 (466G)
   Sectorsize: 512
   Mode: r1w1e3

 

[Zofoor]

Strange thing # 2: If I reboot the server, the free space available is correct.