Comment 6 for bug 1262973

udev in Ubuntu returns the same path ID for all of these ATA devices (CentOS returns unique paths).

root@node-24:/lib/udev# udevadm test-builtin path_id /block/sda/
ID_PATH=pci-0000:00:1f.2-scsi-0:0:0:0
ID_PATH_TAG=pci-0000_00_1f_2-scsi-0_0_0_0
root@node-24:/lib/udev# udevadm test-builtin path_id /block/sdb/
ID_PATH=pci-0000:00:1f.2-scsi-0:0:0:0
ID_PATH_TAG=pci-0000_00_1f_2-scsi-0_0_0_0
root@node-24:/lib/udev# udevadm test-builtin path_id /block/sdc/
ID_PATH=pci-0000:00:1f.2-scsi-0:0:0:0
ID_PATH_TAG=pci-0000_00_1f_2-scsi-0_0_0_0

Therefore only one symlink is created in /dev/disk/by-path. We should use /dev/disk/by-id/ instead which is consistent across CentOS and Ubuntu and then to fall back to /dev/disk/by-path if there is no entry in by-id (this case should only occur when using virtio drives).