Add Physical Drive in Proxmox VM Guest

Step-1:

Check the block disk status-

lsblk

Step-2

Check the blockid of the system-

blkid

Step-3

Now list the device by ID-

ls -n /dev/disk/by-id/

Now add the disk to the Virtual Machine Instance-

/sbin/qm set 105 -virtio1/dev/disk/by-id/ata-HGST_HGH728570ALE604_VKGRZ09X

Here-

105- is the VMID
virtio1- is the disk ID number, assuming the first disk is added as virtio0 and now you're adding the 2nd drive
ata-HGST_HGH728570ALE604_VKGRZ09X- is the device id number discovered on

There’s a lovely video tutorial out there where you may find it in details.