How to monitor LVM with internal dmraid

This document (7017850) is provided subject to the disclaimer at the end of this document.

Environment

SUSE Linux Enterprise Server 12 Service Pack 1 (SLES 12 SP1)

Situation

Getting a status on the monitored devices via "systemctl status lvm2-monitor" will only show devices present at the start of lvm2-monitor.service.
Monitoring is essential for automatic repair of dmraid enabled LV-mirrors.

e.g.

Creating a new LVM ( with dm-raid ):

sles12sp1-node1:~ # vgcreate MIRROR /dev/sdc /dev/sdd
Volume group "MIRROR" successfully created
sles12sp1-node1:~ # lvcreate -m1 -n lvo1 -l 100%VG MIRROR
Logical volume "lvo1" created.
sles12sp1-node1:~ # systemctl status lvm2-monitor
lvm2-monitor.service - Monitoring of LVM2 mirrors, snapshots etc. using dmeventd or progress polling
   Loaded: loaded (/usr/lib/systemd/system/lvm2-monitor.service; enabled)
   Active: active (exited) since Fr 2016-07-15 14:46:30 CEST; 3min 10s ago
     Docs: man:dmeventd(8)
           man:lvcreate(8)
           man:lvchange(8)
           man:vgchange(8)
Process: 2510 ExecStop=/sbin/lvm vgchange --monitor n --ignoreskippedcluster (code=exited, status=0/SUCCESS)
Process: 2513 ExecStart=/sbin/lvm vgchange --monitor y --ignoreskippedcluster (code=exited, status=0/SUCCESS)
Main PID: 2513 (code=exited, status=0/SUCCESS)
   CGroup: /system.slice/lvm2-monitor.service

Jul 15 14:46:30 sles12sp1-node1 lvm[2513]: 1 logical volume(s) in volume group "md-raid" monitored
Jul 15 14:46:30 sles12sp1-node1 systemd[1]: Started Monitoring of LVM2 mirrors, snapshots etc. using dmeventd or progress polling.

The newly created volume does not seem to be monitored.

Resolution

"systemctl status lvm2-monitor" is not the correct tool for the job. Use dmevent_tool instead.

sles12sp1-node1:~ # dmevent_tool -mr
Device Name: MIRROR-lvo1
    Registered DSO:   libdevmapper-event-lvm2raid.so
    UUID:             LVM-cqN9ACOPGJxHCL8I4KIZDbUZRQvWRgTYHrUgzZW1uVhc0G560lkyp2mLkeROSjI7
    Status:           Active
    Major Device #:   253
    Minor Device #:   5
    Read-only Device: No
    Error Events:     1

Cause

The service file lvm2-monitor simply starts monitoring with the command line "vgchange --monitor y ...", but has no way to show
which volumes are monitored, except volumes present at the start of the service.

Additional Information

To make monitoring working the lvm2-lvmetad and lvm2-monitor services have to be enabled, furthermore "use_lvmetad=1" in /etc/lvm/lvm.conf ( default in SLES12 SP1 ) has to be set.

Disclaimer

This Support Knowledgebase provides a valuable tool for SUSE customers and parties interested in our products and solutions to acquire information, ideas and learn from one another. Materials are provided for informational, personal or non-commercial use within your organization and are presented "AS IS" WITHOUT WARRANTY OF ANY KIND.

Document ID:7017850
Creation Date: 15-Jul-2016
Modified Date:03-Mar-2020
- SUSE Linux Enterprise Server
- SUSE Linux Enterprise Server for SAP Applications

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