By listing linked devices in /dev:
root@pluto:~# ls -la /dev/disk/by-path/*iscsi* lrwxrwxrwx 1 root root 9 Dec 6 14:13 /dev/disk/by-path/ip-9.6.9.3:3260-iscsi-iqn.2014-07.ro.gz.sun:backups-btrfs-lun-0 -> ../../sdb lrwxrwxrwx 1 root root 9 Dec 6 14:39 /dev/disk/by-path/ip-9.6.9.3:3260-iscsi-iqn.2014-07.ro.gz.sun:pluto-lun-0 -> ../../sdd lrwxrwxrwx 1 root root 9 Dec 6 14:13 /dev/disk/by-path/ip-9.6.9.4:3260-iscsi-iqn.2014-07.ro.gz.ogle:backups-btrfs-lun-0 -> ../../sdc lrwxrwxrwx 1 root root 9 Dec 6 14:22 /dev/disk/by-path/ip-9.6.9.4:3260-iscsi-iqn.2014-07.ro.gz.ogle:pluto-lun-0 -> ../../sde lrwxrwxrwx 1 root root 10 Dec 6 14:32 /dev/disk/by-path/ip-9.6.9.4:3260-iscsi-iqn.2014-07.ro.gz.ogle:pluto-lun-0-part1 -> ../../sde1