Thanks for your encouragement. I've now filed this as an issue with upstream systemd as https://github.com/systemd/systemd/issues/3943 .
** Bug watch added: github.com/systemd/systemd/issues #3943 https://github.com/systemd/systemd/issues/3943 -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to systemd in Ubuntu. https://bugs.launchpad.net/bugs/1611945 Title: /dev/disk/by-path not properly populated for (e)SATA port multiplier disks Status in systemd package in Ubuntu: New Bug description: We have a just-installed Ubuntu 16.04 LTS machine with a number of disks behind port-multiplier eSATA ports, all of them driven by a SiI 3124 controller (sata_sil24 kernel driver). Our machine sees all disks on all channels, however under 16.04 only one disk from each channel shows up in /dev/disk/by-path/ (all disks show up in /dev/disk/by-id and /dev/disk/by-uuid). For our usage this is a severe defect because we rotate disks in and out of the external enclosure and rely on mounting specific slots in the external enclosure through /dev/disk /by-path. This did not happen in Ubuntu 12.04 LTS, the release that this machine was previously running. According to 'udevadm info --export-db' and 'udevadm test-builtin path_id' and so on, systemd's udev stuff is assigning all drives behind the same port the same disk/by-path data (ID_PATH et al). In 'udevadm info /sys/block/sdX', the 'P:' and 'E: DEVPATH=' values show a difference in the target portion of PCI path, eg: P: /devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:00.0/ata1/host0/target0:0:0/0:0:0:0/block/sda P: /devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:00.0/ata1/host0/target0:1:0/0:1:0:0/block/sdb However the 'S: disk/by-path', 'E: DEVLINKS=', and 'E: ID_PATH' portions do not. For both devices above, we see: S: disk/by-path/pci-0000:02:00.0-ata-1 E: ID_PATH=pci-0000:02:00.0-ata-1 Naturally only one device can have a /dev/disk/by- path/pci-0000:02:00.0-ata-1 symlink, so instead of four disks per channel in /dev/disk/by-path we see one. Ubuntu release: 16.04 Package versions from 'apt-cache policy udev systemd': udev: Installed: 229-4ubuntu7 systemd: Installed: 229-4ubuntu7 'journalctl -b' reports that during boot systemd does report some 'appeared twice with different sysfs paths' notes, eg: Aug 10 13:34:21 verdandi systemd[1]: dev-disk-by\x2dpath- pci\x2d0000:02:00.0\x2data\x2d1\x2dpart1.device: Dev dev-disk-by \x2dpath-pci\x2d0000:02:00.0\x2data\x2d1\x2dpart1.device appeared twice with different sysfs paths /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:00.0/ata1/host0/target0:3:0/0:3:0:0/block/sdd/sdd1 and /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:00.0/ata1/host0/target0:0:0/0:0:0:0/block/sda/sda1 However it doesn't seem to be reporting this for all port-multiplier drives and their partitions. If it would be useful I can attach full 'udevadm info --export-db' output or the like. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1611945/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp
