Installation guide

Creating Snapshot Volumes
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specified by the mirror_log_fault_policy and mirror_device_fault_policy parameters
in the lvm.conf file.
4.4.3.4. Changing Mirrored Volume Configuration
You can convert a logical volume from a mirrored volume to a linear volume or from a linear volume
to a mirrored volume with the lvconvert command. You can also use this command to reconfigure
other mirror parameters of an existing logical volume, such as corelog.
When you convert a logical volume to a mirrored volume, you are basically creating mirror legs for an
existing volume. This means that your volume group must contain the devices and space for the mirror
legs and for the mirror log.
If you lose a leg of a mirror, LVM converts the volume to a linear volume so that you still have access
to the volume, without the mirror redundancy. After you replace the leg, you can use the lvconvert
command to restore the mirror. This procedure is provided in Section 6.3, “Recovering from LVM
Mirror Failure”.
The following command converts the linear logical volume vg00/lvol1 to a mirrored logical volume.
# lvconvert -m1 vg00/lvol1
The following command converts the mirrored logical volume vg00/lvol1 to a linear logical volume,
removing the mirror leg.
# lvconvert -m0 vg00/lvol1
4.4.4. Creating Snapshot Volumes
Use the -s argument of the lvcreate command to create a snapshot volume. A snapshot volume is
writable.
Note
LVM snapshots are not supported across the nodes in a cluster. You cannot create a snapshot
volume in a clustered volume group. As of the Red Hat Enterprise Linux 6.1 release, however, if
you need to create a consistent backup of data on a clustered logical volume you can activate the
volume exclusively and then create the snapshot. For information on activating logical volumes
exclusively on one node, see Section 4.7, “Activating Logical Volumes on Individual Nodes in a
Cluster”.