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+
+.. _ceph-volume-zfs-api:
+
+ZFS
+===
+The backend of ``ceph-volume zfs`` is ZFS, it relies heavily on the usage of
+tags, which is a way for ZFS to allow extending its volume metadata. These
+values can later be queried against devices and it is how they get discovered
+later.
+
+Currently this interface is only usable when running on FreeBSD.
+
+.. 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-zfs-tag-api:
+
+Tag API
+-------
+The process of identifying filesystems, volumes and pools 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 zfs tags::
+
+    ceph.osd_id=0
+
+Tags on filesystems are stored as property.
+Tags on a zpool are stored in the comment property as a concatenated list 
+seperated by ``;`` 
+
+.. _ceph-volume-zfs-tags:
+
+Metadata
+--------
+The following describes all the metadata from Ceph OSDs that is stored on a
+ZFS filesystem, volume, pool:
+
+
+``type``
+--------
+Describes if the device is an OSD or Journal, with the ability to expand to
+other types when supported 
+
+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
+
+
+``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/gpt/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/gpt/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/gpt/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
+
+
+``compression``
+---------------
+A compression-enabled device can allways be set using the native zfs settings on
+a volume or filesystem. This will/can be activated during creation of the volume
+of filesystem. 
+When activated by ``ceph-volume zfs`` this tag will be created.
+Compression manually set AFTER ``ceph-volume`` will go unnoticed, unless this 
+tag is also manually set.
+
+Example for an enabled compression device::
+
+    ceph.vdo=1