6.5. Creating a Mirrored LVM Logical Volume in a Cluster Creating a mirrored LVM logical volume in a cluster requires the same commands and procedures as creating a mirrored LVM logical volume on a single node. However, in order to create a mirrored LVM volume in a cluster the cluster and cluster mirror infrastructure must be running, the cluster must be quorate, and the locking type in the lvm.conf file must be set correctly to enable cluster locking, either directly or by means of the lvmconf command as described in Section 4.1, "Creating LVM Volumes in a Cluster" . The following procedure creates a mirrored LVM volume in a cluster. First the procedure checks to see whether the cluster services are installed and running, then the procedure creates the mirrored volume. In order to create a mirrored logical volume that is shared by all of the nodes in a cluster, the locking type must be set correctly in the lvm.conf file in every node of the cluster. By default, the locking type is set to local. To change this, execute the following command in each node of the cluster to enable clustered locking: Note As of Red Hat Enterprise Linux 6.7, the lvmconf command provides a --services option that will also enable the services required for LVM in a cluster, a --mirrorservice option that enables the cmirrord service, and a --startstopservices option that immediately starts or stops the services that have been enabled. For information on the lvmconf command, see the lvmconf man page. To create a clustered logical volume, the cluster infrastructure must be up and running on every node in the cluster. The following example verifies that the clvmd daemon is running on the node from which it was issued: The following command shows the local view of the cluster status: Ensure that the cmirror package is installed. Start the cmirrord service. Create the mirror. The first step is creating the physical volumes. The following commands create three physical volumes. Two of the physical volumes will be used for the legs of the mirror, and the third physical volume will contain the mirror log. Create the volume group. This example creates a volume group vg001 that consists of the three physical volumes that were created in the step. Note that the output of the vgcreate command indicates that the volume group is clustered. You can verify that a volume group is clustered with the vgs command, which will show the volume group's attributes. If a volume group is clustered, it will show a c attribute. Create the mirrored logical volume. This example creates the logical volume mirrorlv from the volume group vg001 . This volume has one mirror leg. This example specifies which extents of the physical volume will be used for the logical volume. You can use the lvs command to display the progress of the mirror creation. The following example shows that the mirror is 47% synced, then 91% synced, then 100% synced when the mirror is complete. The completion of the mirror is noted in the system log: You can use the lvs with the -o +devices options to display the configuration of the mirror, including which devices make up the mirror legs. You can see that the logical volume in this example is composed of two linear images and one log. You can use the seg_pe_ranges option of the lvs to display the data layout. You can use this option to verify that your layout is properly redundant. The output of this command displays PE ranges in the same format that the lvcreate and lvresize commands take as input. Note For information on recovering from the failure of one of the legs of an LVM mirrored volume, see Section 7.3, "Recovering from LVM Mirror Failure" .

Commands:
/sbin/lvmconf --enable-cluster
ps auxw | grep clvmd root 17642 0.0 0.1 32164 1072 ? Ssl Apr06 0:00 clvmd -T20 -t 90
cman_tool services fence domain member count 3 victim count 0 victim now 0 master nodeid 2 wait state none members 1 2 3 dlm lockspaces name clvmd id 0x4104eefa flags 0x00000000 change member 3 joined 1 remove 0 failed 0 seq 1,1 members 1 2 3
service cmirrord start Starting cmirrord: [ OK ]
pvcreate /dev/sdb1 Physical volume "/dev/sdb1" successfully created pvcreate /dev/sdc1 Physical volume "/dev/sdc1" successfully created pvcreate /dev/sdd1 Physical volume "/dev/sdd1" successfully created
vgcreate vg001 /dev/sdb1 /dev/sdc1 /dev/sdd1 Clustered volume group "vg001" successfully created
vgs vg001 VG #PV #LV #SN Attr VSize VFree vg001 3 0 0 wz--nc 68.97G 68.97G
lvcreate -l 1000 -m1 vg001 -n mirrorlv /dev/sdb1:1-1000 /dev/sdc1:1-1000 /dev/sdd1:0 Logical volume "mirrorlv" created
lvs vg001/mirrorlv LV VG Attr LSize Origin Snap% Move Log Copy% Convert mirrorlv vg001 mwi-a- 3.91G vg001_mlog 47.00 lvs vg001/mirrorlv LV VG Attr LSize Origin Snap% Move Log Copy% Convert mirrorlv vg001 mwi-a- 3.91G vg001_mlog 91.00 lvs vg001/mirrorlv LV VG Attr LSize Origin Snap% Move Log Copy% Convert mirrorlv vg001 mwi-a- 3.91G vg001_mlog 100.00
May 10 14:52:52 doc-07 [19402]: Monitoring mirror device vg001-mirrorlv for events May 10 14:55:00 doc-07 lvm[19402]: vg001-mirrorlv is now in-sync
lvs -a -o +devices LV VG Attr LSize Origin Snap% Move Log Copy% Convert Devices mirrorlv vg001 mwi-a- 3.91G mirrorlv_mlog 100.00 mirrorlv_mimage_0(0),mirrorlv_mimage_1(0) [mirrorlv_mimage_0] vg001 iwi-ao 3.91G /dev/sdb1(1) [mirrorlv_mimage_1] vg001 iwi-ao 3.91G /dev/sdc1(1) [mirrorlv_mlog] vg001 lwi-ao 4.00M /dev/sdd1(0)
lvs -a -o +seg_pe_ranges --segments PE Ranges mirrorlv_mimage_0:0-999 mirrorlv_mimage_1:0-999 /dev/sdb1:1-1000 /dev/sdc1:1-1000 /dev/sdd1:0-0