Pretty sure you meant to say "I don't know why..."

Anyhow, LQ is mangling URLs that end in a round bracket. You can fix it manually after LQ created the [url]...[/url] tags:
https://pve.proxmox.com/wiki/Passthr...l_Machine_(VM)

because the 2 are the same point

these are df -h of the 2 machines, even from what I see they don't even match the percentages of use for that I put below the uuid of the disks and you can see that they are exactly the same


machines 1

S.ficheros Tamaño Usados Disp Uso% Montado en
/dev/sda2 94G 14G 76G 16% /
/dev/sdb1 21T 12T 8,8T 56% /mnt/back
10.70.9.60:/backups 1,8T 1,4T 331G 81% /maquina_bakups

blkid
/dev/sdb1: UUID="17799b02-1134-4102-9c86-1ea11adde8f3" TYPE="ext4" PARTUUID="a7017e92-63d4-f448-9c3c-b5b8a88475b7"


machines 2

S.ficheros Tamaño Usados Disp Uso% Montado en
/dev/sda3 490G 140G 325G 31% /
/dev/sdb1 21T 7,7T 13T 39% /mnt/datos
/dev/sda2 473M 86M 363M 20% /boot
/dev/sda1 511M 3,3M 508M 1% /boot/efi


blkid
/dev/sdb1: UUID="17799b02-1134-4102-9c86-1ea11adde8f3" TYPE="ext4" PARTUUID="a7017e92-63d4-f448-9c3c-b5b8a88475b7"


this topic really drives me crazy

ok, so you stated the following:
How /dev/sdb1 is mounted? (local or remote on machine1 and machine2)?


I guess there is a cache somewhere and when you access /dev/sdb1 on machine1 the other one does not recognize the change and still use the old data from cache.
You might need to invalidate that cache. But actually we don't know this setup (how this drive is shared/mounted), so I'm not really sure about that.

Normal filesystems cannot be mounted on multiple systems. They have no support for shared access. The best filesystem to do this on Linux is probably GFS2. https://en.wikipedia.org/wiki/GFS2

And based on what's posted here, this is absolutely a continuation of the OP's other thread regarding backups:
https://www.linuxquestions.org/quest...ds-4175710171/

Given that the op posted this (bolded for emphasis only):
OP, given the fact you have JUST NOW SAID (after two threads, and 18 posts in this one), that the second machine is a VM **ON THE FIRST** is a good reason for you to actually answer questions. Think about what you're saying: you're trying to mount a disk on machine 1...from another machine that is ALSO on machine 1. You're still trying to mount the same resource that's already mounted.

That, plus the fact you're not giving any details and keep opening threads about the same system, apparently thinking no one here is going to notice.