The software described in this documentation is either in Extended Support or Sustaining Support. See https://www.oracle.com/us/support/library/enterprise-linux-support-policies-069172.pdf for more information.
Oracle recommends that you upgrade the software described by this documentation as soon as possible.
Having create a volume group of physical volumes, you can create logical volumes from the storage space that is available in the volume group.
To create a logical volume, use the lvcreate command:
#lvcreate
[options
]--size
size
--name
logical_volume
volume_group
For example, create the logical volume mylv
of size 2 GB in the volume group myvg
:
# lvcreate -v --size 2g --name mylv myvg
Setting logging type to disk
Finding volume group “myvg”
Archiving volume group “myvg” metadata (seqno 1).
Creating logical volume mylv
Create volume group backup “/etc/lvm/backup/myvg” (seqno 2).
...
lvcreate uses the device mapper to create a
block device file entry under /dev
for each
logical volume and uses udev to set up symbolic links to this
device file from /dev/mapper
and
/dev/
volume_group
.
For example, the device that corresponds to the logical volume
mylv
in the volume group
myvg
might be /dev/dm-3
,
which is symbolically linked by
/dev/mapper/myvolg-myvol
and
/dev/myvolg/myvol
.
Always use the devices in /dev/mapper
or
/dev/
volume_group
.
These names are persistent and are created automatically by
the device mapper early in the boot process. The
/dev/dm-*
devices are not guaranteed to be
persistent across reboots.
Having created a logical volume, you can configure and use it in the same way as you would a physical storage device. For example, you can configure a logical volume as a file system, swap partition, Automatic Storage Management (ASM) disk, or raw device.
You can also use lvcreate to create a
snapshot of an existing logical volume such as
mylv
in the volume group
myvg
, for example:
# lvcreate --size 500m --snapshot --name mylv-snapshot myvg/mylv
Logical volume “mylv-snapshot” created
You can mount and modify the contents of the snapshot
independently of the original volume or preserve it as a record
of the state of the original volume at the time that you took
the snapshot. The snapshot usually takes up less space than the
original volume, depending on how much the contents of the
volumes diverge over time. In the example, we assume that the
snapshot only requires one quarter of the space of the original
volume. You can use the value shown by the
Snap%
column in the output from the
lvs command to see how much data is allocated
to the snapshot. If the value of Snap%
approaches 100%, indicating that a snapshot is running out of
storage, use lvresize to grow it.
Alternatively, you can reduce a snapshot's size to save storage
space. To merge a snapshot with its original volume, use the
lvconvert command, specifying the
--merge option.
To display information about logical volumes, you can use the lvdisplay, lvs, and lvscan commands.
To remove a logical volume from a volume group, use the lvremove command:
#lvremove
volume_group
/
logical_volume
You must specify both the name of the volume group and the logical volume.
Other commands that are available for managing logical volumes include lvchange, lvconvert, lvmdiskscan, lvmsadc, lvmsar, lvrename, and lvresize.
For more information, see the lvm(8)
,
lvcreate(8)
, and other LVM manual pages.