Given a Proxmox pool's STORAGE_ID in $poolid
pvesm list $poolid | awk 'NR>1 {print $1}' | \
while read -r volid
do echo -n "Finding ID_SERIAL for $volid..."
serial=$(pvesm path "$volid" 2>/dev/null | grep -v "^Rescanning" | sed -r "s|iscsi://([0-9.]+)/([^:]+):([^/]+)/([0-9]+)|/dev/disk/by-path/ip-\1\\:3260-iscsi-\2\\:\3-lun-\4|" | xargs -I{} udevadm info {} 2>/dev/null | grep ID_SERIAL= | sed -r "s|^.*ID_SERIAL=([0-9a-fA-F]+).$|\1|" || echo "No ID_SERIAL found for volid $volid")
multipath -a "$serial"
done