<commit_before>===================================
Back up Block Storage service disks
===================================

While you can use the LVM snapshot to create snapshots, you can also use
it to back up your volumes. By using LVM snapshot, you reduce the size
of the backup; only existing data is backed up instead of the entire
volume.

To back up a volume, you must create a snapshot of it. An LVM snapshot
is the exact copy of a logical volume, which contains data in a frozen
state. This prevents data corruption because data cannot be manipulated
during the volume creation process. Remember that the volumes created
through a :command:`nova volume-create` command exist in an LVM logical
volume.

You must also make sure that the operating system is not using the
volume and that all data has been flushed on the guest file systems.
This usually means that those file systems have to be unmounted during
the snapshot creation. They can be mounted again as soon as the logical
volume snapshot has been created.

Before you create the snapshot you must have enough space to save it.
As a precaution, you should have at least twice as much space as the
potential snapshot size. If insufficient space is available, the snapshot<commit_msg>[admin-guide] Legacy to OpenStack command<commit_after>===================================
Back up Block Storage service disks
===================================

While you can use the LVM snapshot to create snapshots, you can also use
it to back up your volumes. By using LVM snapshot, you reduce the size
of the backup; only existing data is backed up instead of the entire
volume.

To back up a volume, you must create a snapshot of it. An LVM snapshot
is the exact copy of a logical volume, which contains data in a frozen
state. This prevents data corruption because data cannot be manipulated
during the volume creation process. Remember that the volumes created
through an :command:`openstack volume create` command exist in an LVM
logical volume.

You must also make sure that the operating system is not using the
volume and that all data has been flushed on the guest file systems.
This usually means that those file systems have to be unmounted during
the snapshot creation. They can be mounted again as soon as the logical
volume snapshot has been created.

Before you create the snapshot you must have enough space to save it.
As a precaution, you should have at least twice as much space as the
potential snapshot size. If insufficient space is available, the snapshot
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