LVM excludes physical volume as multipath device even after multipath blacklisting

SUSE Linux Enterprise Server 15 SP6 and earlier
SUSE Linux Enterprise Server for SAP Applications 15 SP6 and earlier

LVM does not use some physical volumes even when they are present and can be accessed. (As seen with `lsblk', `lsscsi' etc...)
During scan for the physical volumes it skips some devices/partitions considering them as a part of multipath device while in fact they are not.

The simplest way to fix this is by removing the device wwid from multipah configuration files and rebooting.

To fix this without rebooting following steps should be followed:

1. remove device from /etc/multipath/wwids file if listed there
2. excluded it via `multipath.conf(5)' blacklist option
3. update it's udev attributes

An example (you need to only follow the first two steps and reboot or follow them all without rebooting)

1. query the SCSI device identifier/wwn
   /usr/lib/udev/scsi_id -g /dev/disk/by-id/scsi-example1:f1a4e576-3289-4a3e-9308-28087baf773b
36001405c1a4e9163f69463e910848087

2. remove the SCSI device identifier/wwn from wwdis file
   multipath -w 36001405c1a4e9163f69463e910848087
3. blacklist the device via SCSI device identifier/wwn
   cat > /etc/multipath/conf.d/my_blacklist.conf <<EOF
blacklist {
wwid 36001405c1a4e9163f69463e910848087
}
EOF
4. reconfigure the multipaths
   multipathd reconfigure
5. trigger udev reconfiguration for the device
   udevadm trigger /dev/disk/by-id/scsi-example1:f1a4e576-3289-4a3e-9308-28087baf773b

LVM by default has multipath detection enabled in /etc/lvm/lvm.conf.

The LVM does this by 

• checking the sysfs of the device
• checking presence of the device's SCSI identifier in /etc/multipath/wwids file
• checking the udev DM_MULTPATH_DEVICE_PATH attribute

If the multipath detection comes back positive the device is skipped during physical volume lvm scan.

As of SLE 15 SP6 codestream even if you blacklist the previously multipathed device and reconfigure the multipath daemon that does not trigger udev reconfiguration and the udev attribute may still be present. This is scheduled to be fixed in the future SLE versions.

LVM `pvscan -vvv' might show similar lines for devices previously being the PVs, which are currently not "visible":

/dev/disk/by-id/scsi-example1:f1a4e576-3289-4a3e-9308-28087baf773b: size is 2097152 sectors
  Closed /dev/disk/by-id/scsi-example1:f1a4e576-3289-4a3e-9308-28087baf773b
  dev_is_mpath_component /dev/disk/by-id/scsi-example1:f1a4e576-3289-4a3e-9308-28087baf773b naa.6001405af74e9163f69463e910848087 in wwids file
  /dev/disk/by-id/scsi-example1:f1a4e576-3289-4a3e-9308-28087baf773b: Skipping mpath component device

The device above is skipped because the device SCSI identifier is present in /etc/multipath/wwids file.

# query of the SCSI device identifier/wwn

$ /usr/lib/udev/scsi_id -g /dev/disk/by-id/scsi-example1:f1a4e576-3289-4a3e-9308-28087baf773b
36001405c1a4e9163f69463e910848087

$ grep 36001405c1a4e9163f69463e910848087 /etc/multipath/wwids 
/36001405c1a4e9163f69463e910848087/

The device still might have UDEV attribute DM_MULTIPATH_DEVICE_PATH=1:

$ udevadm info -n \
  /dev/disk/by-id/scsi-example1:f1a4e576-3289-4a3e-9308-28087baf773b \
  | grep DM_MULTIPATH_DEVICE_PATH
E: DM_MULTIPATH_DEVICE_PATH=1