Cannot activate LVs in VG <vg_name> while PVs appear on duplicate devices

Environment

• Red Hat Enterprise Linux 8
• LVM2
• Multiple paths to storage device(s)

Issue

• Cannot activate the volume group.

[root@testbox lvm]# vgchange -ay testvg
  WARNING: Not using device /dev/sde1 for PV pv_uuid.
  WARNING: Not using device /dev/sdf1 for PV pv_uuid.
  WARNING: Not using device /dev/sdg1 for PV pv_uuid.
  Cannot activate LVs in VG testvg while PVs appear on duplicate devices.  <<<<
  0 logical volume(s) in volume group "testvg" now active  <<<<

• Why do I get duplicate PV warnings when I run LVM commands?

Resolution

• Configure the multipath and set the LVM filter to fix the issue.

Root Cause

The allow_changes_with_duplicate_pvs config option within lvm.conf is set to boolean value 0 in RHEL 8. This change disallows a VG to activate/change while duplicate PV's are detected to protect from metadata corruption.

	# Configuration option devices/allow_changes_with_duplicate_pvs.
	# Allow VG modification while a PV appears on multiple devices.
	# When a PV appears on multiple devices, LVM attempts to choose the
	# best device to use for the PV. If the devices represent the same
	# underlying storage, the choice has minimal consequence. If the
	# devices represent different underlying storage, the wrong choice
	# can result in data loss if the VG is modified. Disabling this
	# setting is the safest option because it prevents modifying a VG
	# or activating LVs in it while a PV appears on multiple devices.
	# Enabling this setting allows the VG to be used as usual even with
	# uncertain devices.
	allow_changes_with_duplicate_pvs = 0

Diagnostic Steps

• Messages logs are pilled up with duplicate PV messages:

Nov 25 18:52:33 testbox lvm[1371]:  WARNING: PV pv_uuid prefers device /dev/sdc because device was seen first.
Nov 25 18:52:33 testbox lvm[1717]:  Cannot activate LVs in VG <vg_name> while PVs appear on duplicate devices.
Nov 25 18:52:33 testbox lvm[1717]:  Cannot activate LVs in VG  <vg_name> while PVs appear on duplicate devices.

• Verify allow_changes_with_duplicate_pvs value in lvm.conf file:

 # cat etc/lvm/lvm.conf| grep allow_changes_with_duplicate_pvs| egrep  -v "#|^$"
   allow_changes_with_duplicate_pvs = 0

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