I’ve added 2 external USBs of 2TB each to my Proxmox server and created a Resource Pool called USB_HDD containing both. I created an Ubuntu VM, but I can’t allocate all 4TB to it in one go - it only allows me to add each one as a separate SCSI device. When I start to install the OS it only allows the install onto one of the 2TB devices. I though the point of pools was to make the actual disks transparent, and present the pool to the VM so it sees it as one lot of space. Am I doing something wrong, or do I have to have it as 2x2TB disks?
I think the question is if you want to add the external USB hard drives to Proxmox so that not just the mentioned Ubuntu VM but other VMs and LXCs can benefit from them or if you want them to be added exclusively to the Ubuntu VM and Ubuntu VM only.
If it is the latter, you can leverage USB device passthrough and passthrough the two drives to the VM in whole. Then you can do whatever you want with them inside the VM. You can use ZFS or BTRFS or mdadm to create a stripe aka RAID 0 config.