Why is free space on mounted drives decreasing?

Question

Proxmox

Proxmox 4.4-87
Installing and configuring according to the manual
https://serveradmin.ru/ustanovka-i-nastroyka-proxmox/
Debian 8.7 guest OS
Over the past couple of months, the free space on the mounted array md1 Raid 1 has been decreasing very quickly
We look at the free space shown by Proxmox
/dev/md0 5.5T 1.8T 3.4T 35% /mnt/md0
/dev/md1 5.5T 4.9T 262G 96% /mnt/md1
We look at the free one that shows the Debian 8.7 guest OS where these arrays are mounted
/dev/sdc 5.3T 1.6 T 3.5T 32% /mnt/md1
/dev/sdb 5.3T 2.8T 2.2T 56% /mnt/md0
The web interface has slightly different information
md0 Usage32.30% (1.75 TiB of 5.41 TiB)
md1 Usage90.25% (4.89 TiB of 5.41 TiB)
It's not entirely clear why Proxmox shows that the md1 array is running out of space when the guest OS still has space on the md1 array.
Can anyone come across?

Answer 1

because the place is occupied by the wrong guest wasps or backups or some other garbage.
look through the doo what the place is occupied