Comment # 6 on bug 1099391 from Michael Hanscho

Addition:

When boot fails you end up in emergency mode.
An error message before the emergency mode states:
"Failed to start LVM2 PV scan on device 9:126" and check details using command:
"systemctl status lvm2-pvscan@9:126"

When running "systemctl status lvm2-pvscan@9:126", following output can be
found:
 lvm2-pvscan@9:126.service - LVM2 PV scan on device 9:126
   Loaded: loaded (/usr/lib/systemd/system/lvm2-pvscan@.service; static; vendor
preset: disabled)
   Active: failed (Result: exit-code) since Tue 2018-10-09 23:20:04 CEST; 4min
26s ago
     Docs: man:pvscan(8)
  Process: 861 ExecStart=/usr/sbin/lvm pvscan --cache --activate ay 9:126
(code=exited, status=5)
 Main PID: 861 (code=exited, status=5)

Oct 09 23:20:04 linux-dnetctw lvm[861]:   /dev/sde: open failed: No medium
found
Oct 09 23:20:04 linux-dnetctw lvm[861]:   WARNING: Not using device /dev/sdc2
for PV qG1QRz-Ivm1-QVwq-uaHV-va9w-wwXh-lIIOhV.
Oct 09 23:20:04 linux-dnetctw lvm[861]:   WARNING: Not using device /dev/md126
for PV qG1QRz-Ivm1-QVwq-uaHV-va9w-wwXh-lIIOhV.
Oct 09 23:20:04 linux-dnetctw lvm[861]:   WARNING: PV
qG1QRz-Ivm1-QVwq-uaHV-va9w-wwXh-lIIOhV prefers device /dev/sdb2 because of
previous preference.
Oct 09 23:20:04 linux-dnetctw lvm[861]:   Cannot activate LVs in VG vghome
while PVs appear on duplicate devices.
Oct 09 23:20:04 linux-dnetctw lvm[861]:   0 logical volume(s) in volume group
"vghome" now active
Oct 09 23:20:04 linux-dnetctw lvm[861]:   vghome: autoactivation failed.
Oct 09 23:20:04 linux-dnetctw systemd[1]: lvm2-pvscan@9:126.service: Main
process exited, code=exited, status=5/NOTINSTALLED
Oct 09 23:20:04 linux-dnetctw systemd[1]: lvm2-pvscan@9:126.service: Failed
with result 'exit-code'.
Oct 09 23:20:04 linux-dnetctw systemd[1]: Failed to start LVM2 PV scan on
device 9:126.

Gruesse
Michael