Installation guide

Chapter 4. LVM Administration with CLI Commands
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Note
As of the Red Hat Enterprise Linux 6.1 release, LVM snapshots are supported for mirrored logical
volumes.
The following command creates a snapshot logical volume that is 100 MB in size named /dev/
vg00/snap. This creates a snapshot of the origin logical volume named /dev/vg00/lvol1. If
the original logical volume contains a file system, you can mount the snapshot logical volume on an
arbitrary directory in order to access the contents of the file system to run a backup while the original
file system continues to get updated.
# lvcreate --size 100M --snapshot --name snap /dev/vg00/lvol1
After you create a snapshot logical volume, specifying the origin volume on the lvdisplay command
yields output that includes a list of all snapshot logical volumes and their status (active or inactive).
The following example shows the status of the logical volume /dev/new_vg/lvol0, for which a
snapshot volume /dev/new_vg/newvgsnap has been created.
# lvdisplay /dev/new_vg/lvol0
--- Logical volume ---
LV Name /dev/new_vg/lvol0
VG Name new_vg
LV UUID LBy1Tz-sr23-OjsI-LT03-nHLC-y8XW-EhCl78
LV Write Access read/write
LV snapshot status source of
/dev/new_vg/newvgsnap1 [active]
LV Status available
# open 0
LV Size 52.00 MB
Current LE 13
Segments 1
Allocation inherit
Read ahead sectors 0
Block device 253:2
The lvs command, by default, displays the origin volume and the current percentage of the snapshot
volume being used for each snapshot volume. The following example shows the default output for
the lvs command for a system that includes the logical volume /dev/new_vg/lvol0, for which a
snapshot volume /dev/new_vg/newvgsnap has been created.
# lvs
LV VG Attr LSize Origin Snap% Move Log Copy%
lvol0 new_vg owi-a- 52.00M
newvgsnap1 new_vg swi-a- 8.00M lvol0 0.20