[linux-lvm] PV not found

[John Stoffel]

Giuseppe> after a reboot after a maintenance power interruption of a
Giuseppe> few hours, one of my LVs is not coming back (Ubuntu
Giuseppe> 18.04). The situation I am at is the following:

Ouch, this isn't fun.  

Giuseppe> - the physical disk is an iSCSI and it is seen by the kernel as /dev/sdc

Does it have any partitions on it?  Is this the only iSCSI volume on
the system?  

Giuseppe> - lvmdiskscan -v sees the PV on /dev/sdc
Giuseppe>   /dev/sdc              [      72.76 TiB] LVM physical volume

Can you show the full details of all your LVMs please?  Do any of the
others have a conflict with this device?

Giuseppe> - blkid returns the UUID that I can also find in the LVM configuration
Giuseppe>  /dev/sdc: UUID="fvUXXf-pVOF-EPnn-c8eg-tZ5S-iMVW-wsSFDy" TYPE="LVM2_member"

That's good.  What about if you do:

       pvchange -v /dev/sdc

what happens then?  

Giuseppe> - this entry lacks a PARTUUID entry that other LVs on the
Giuseppe> system have. Is this a clue? I could not quite connect this
Giuseppe> piece of info with anything.

Can you show the full output and the differences?

Giuseppe> - pvscan does not report /dev/sdc

Not good.

Giuseppe> - pvdisplay does not seem to know about this PV
Giuseppe>   pvdisplay /dev/sdc
Giuseppe>   Failed to find physical volume "/dev/sdc"

Not good either. How about the 'pvchange' and/or 'vgchange -ay' as
well?  Maybe the iSCSI LUN is getting mapped after all the rest of the
LVM setup happens...

Giuseppe> Reading man pages and searching the web does not really
Giuseppe> bring me closer to understanding what is happening. This
Giuseppe> machine has its OS on LVs and those have all come back, and
Giuseppe> of course it is not the first time that I reboot. Probably I
Giuseppe> lack the correct terms to describe the problem so that I can
Giuseppe> find a solution. Anybody here on this list who can point me
Giuseppe> in the right direction?

By any chance did you put a partition table on there?  What system is
the iSCSI LUN being exported from?  Can you run the following iscsiadm
command and share the details?

 iscsiadm --mode discoverydb --type sendtargets --portal <IP> --discover

where <IP> is the address of the iSCSI server you're mounting from.
Did that server go down as well?

Good luck!
John