Typically with LVM disks you can just press the resize button in Proxmox and you won’t have any problems. Of course, if you’re using an operating system disk, you still have to perform the resize.
However, when you’re running TrueNAS Scale as an iSCSI NAS, you’ll end up with the following situation straight after the resize:
user@server:~/backup$ mkdir t mkdir: cannot create directory ‘t’: Read-only file system
Yep, unfortunately the disk breaks, and / or kicks into protection mode.
Solution?
I don’t have one.