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+
+.. _ceph-volume-lvm-api:
+
+LVM
+===
+The backend of ``ceph-volume lvm`` is LVM, it relies heavily on the usage of
+tags, which is a way for LVM to allow extending its volume metadata. These
+values can later be queried against devices and it is how they get discovered
+later.
+
+.. warning:: These APIs are not meant to be public, but are documented so that
+             it is clear what the tool is doing behind the scenes. Do not alter
+             any of these values.
+
+
+.. _ceph-volume-lvm-tag-api:
+
+Tag API
+-------
+The process of identifying logical volumes as part of Ceph relies on applying
+tags on all volumes. It follows a naming convention for the namespace that
+looks like::
+
+    ceph.<tag name>=<tag value>
+
+All tags are prefixed by the ``ceph`` keyword to claim ownership of that
+namespace and make it easily identifiable. This is how the OSD ID would be used
+in the context of lvm tags::
+
+    ceph.osd_id=0
+
+
+.. _ceph-volume-lvm-tags:
+
+Metadata
+--------
+The following describes all the metadata from Ceph OSDs that is stored on an
+LVM volume:
+
+
+``type``
+--------
+Describes if the device is an OSD or Journal, with the ability to expand to
+other types when supported (for example a lockbox)
+
+Example::
+
+    ceph.type=osd
+
+
+``cluster_fsid``
+----------------
+Example::
+
+    ceph.cluster_fsid=7146B649-AE00-4157-9F5D-1DBFF1D52C26
+
+
+``data_device``
+---------------
+Example::
+
+    ceph.data_device=/dev/ceph/data-0
+
+
+``data_uuid``
+-------------
+Example::
+
+    ceph.data_uuid=B76418EB-0024-401C-8955-AE6919D45CC3
+
+
+``journal_device``
+------------------
+Example::
+
+    ceph.journal_device=/dev/ceph/journal-0
+
+
+``journal_uuid``
+----------------
+Example::
+
+    ceph.journal_uuid=2070E121-C544-4F40-9571-0B7F35C6CB2B
+
+
+``encrypted``
+-------------
+Example for enabled encryption with ``luks``::
+
+    ceph.encrypted=1
+
+When encryption is not supported or simply disabled::
+
+    ceph.encrypted=0
+
+
+``osd_fsid``
+------------
+Example::
+
+    ceph.osd_fsid=88ab9018-f84b-4d62-90b4-ce7c076728ff
+
+
+``osd_id``
+----------
+Example::
+
+    ceph.osd_id=1
+
+
+``block_device``
+----------------
+Just used on :term:`bluestore` backends. Captures the path to the logical
+volume path.
+
+Example::
+
+    ceph.block_device=/dev/mapper/vg-block-0
+
+
+``block_uuid``
+--------------
+Just used on :term:`bluestore` backends. Captures either the logical volume UUID or
+the partition UUID.
+
+Example::
+
+    ceph.block_uuid=E5F041BB-AAD4-48A8-B3BF-31F7AFD7D73E
+
+
+``db_device``
+-------------
+Just used on :term:`bluestore` backends. Captures the path to the logical
+volume path.
+
+Example::
+
+    ceph.db_device=/dev/mapper/vg-db-0
+
+
+``db_uuid``
+-----------
+Just used on :term:`bluestore` backends. Captures either the logical volume UUID or
+the partition UUID.
+
+Example::
+
+    ceph.db_uuid=F9D02CF1-31AB-4910-90A3-6A6302375525
+
+
+``wal_device``
+--------------
+Just used on :term:`bluestore` backends. Captures the path to the logical
+volume path.
+
+Example::
+
+    ceph.wal_device=/dev/mapper/vg-wal-0
+
+
+``wal_uuid``
+------------
+Just used on :term:`bluestore` backends. Captures either the logical volume UUID or
+the partition UUID.
+
+Example::
+
+    ceph.wal_uuid=A58D1C68-0D6E-4CB3-8E99-B261AD47CC39
+
+
+``vdo``
+-------
+A VDO-enabled device is detected when device is getting prepared, and then
+stored for later checks when activating. This affects mount options by
+appending the ``discard`` mount flag, regardless of mount flags being used.
+
+Example for an enabled VDO device::
+
+    ceph.vdo=1