Comment # 6 on bug 989871 from Liuhua Wang

(In reply to Neil Rickert from comment #5)
> Created attachment 685640 [details]
> Typescript "transcript file" with most of the requested information.
> 
> There no unusual network device.
> 
> I generated the requested output, except "/etc/lvm/lvm.conf".  That file is
> as
> originally installed, except the change to "use_lvmetad = 0".
> 
> After generating the transcript file, I edited "lvm.conf" and set
> "use_lvmetad = 1" (as in the originally installed version).  My plan was to
> reboot, and rerun those commands from emergency mode.
> 
> Strangely, the system booted properly this time.  It did not go into
> emergency mode.  The I appended to the "typescript" and reran "lsblk", as
> the order for the LVM components was now changed.  I have since rebooted a
> second time, and again it did not go into emergency mode.  I do not know
> what changed.  The only significant change that I have made was to install
> "fvwm2" and "fvwm-themes".
Should have no relationship with fvwm. 

As to lvm2-pvscan@, in your case it should be:

 systemctl status lvm2-pvscan@8:21.service  (physical volume's major&minor, not
logical volume's)

I suspect the services are not initialized during boot in case of failure.
If you can still reproduce, please check:

 systemctl status lvm2-lvmetad.socket lvm2-lvmetad.servcie  
 systemctl status lvm2-pvscan@8:21.service 

Thank you!