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93 lines
3.5 KiB
ReStructuredText
93 lines
3.5 KiB
ReStructuredText
.. _ceph-volume-lvm-activate:
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``activate``
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============
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Once :ref:`ceph-volume-lvm-prepare` is completed, and all the various steps
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that entails are done, the volume is ready to get "activated".
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This activation process enables a systemd unit that persists the OSD ID and its
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UUID (also called ``fsid`` in Ceph CLI tools), so that at boot time it can
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understand what OSD is enabled and needs to be mounted.
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.. note:: The execution of this call is fully idempotent, and there is no
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side-effects when running multiple times
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New OSDs
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--------
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To activate newly prepared OSDs both the :term:`OSD id` and :term:`OSD uuid`
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need to be supplied. For example::
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ceph-volume activate --bluestore 0 0263644D-0BF1-4D6D-BC34-28BD98AE3BC8
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.. note:: The UUID is stored in the ``osd_fsid`` file in the OSD path, which is
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generated when :ref:`ceph-volume-lvm-prepare` is used.
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requiring uuids
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^^^^^^^^^^^^^^^
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The :term:`OSD uuid` is being required as an extra step to ensure that the
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right OSD is being activated. It is entirely possible that a previous OSD with
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the same id exists and would end up activating the incorrect one.
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Discovery
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---------
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With OSDs previously created by ``ceph-volume``, a *discovery* process is
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performed using :term:`LVM tags` to enable the systemd units.
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The systemd unit will capture the :term:`OSD id` and :term:`OSD uuid` and
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persist it. Internally, the activation will enable it like::
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systemctl enable ceph-volume@lvm-$id-$uuid
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For example::
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systemctl enable ceph-volume@lvm-0-8715BEB4-15C5-49DE-BA6F-401086EC7B41
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Would start the discovery process for the OSD with an id of ``0`` and a UUID of
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``8715BEB4-15C5-49DE-BA6F-401086EC7B41``.
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.. note:: for more details on the systemd workflow see :ref:`ceph-volume-systemd`
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The systemd unit will look for the matching OSD device, and by looking at its
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:term:`LVM tags` will proceed to:
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# mount the device in the corresponding location (by convention this is
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``/var/lib/ceph/osd/<cluster name>-<osd id>/``)
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# ensure that all required devices are ready for that OSD. In the case of
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a journal (when ``--filestore`` is selected) the device will be queried (with
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``blkid`` for partitions, and lvm for logical volumes) to ensure that the
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correct device is being linked. The symbolic link will *always* be re-done to
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ensure that the correct device is linked.
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# start the ``ceph-osd@0`` systemd unit
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.. note:: The system infers the objectstore type (filestore or bluestore) by
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inspecting the LVM tags applied to the OSD devices
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Existing OSDs
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-------------
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For exsiting OSDs that have been deployed with different tooling, the only way
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to port them over to the new mechanism is to prepare them again (losing data).
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See :ref:`ceph-volume-lvm-existing-osds` for details on how to proceed.
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Summary
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-------
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To recap the ``activate`` process for :term:`bluestore`:
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#. require both :term:`OSD id` and :term:`OSD uuid`
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#. enable the system unit with matching id and uuid
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#. Create the ``tmpfs`` mount at the OSD directory in
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``/var/lib/ceph/osd/$cluster-$id/``
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#. Recreate all the files needed with ``ceph-bluestore-tool prime-osd-dir`` by
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pointing it to the OSD ``block`` device.
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#. the systemd unit will ensure all devices are ready and linked
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#. the matching ``ceph-osd`` systemd unit will get started
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And for :term:`filestore`:
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#. require both :term:`OSD id` and :term:`OSD uuid`
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#. enable the system unit with matching id and uuid
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#. the systemd unit will ensure all devices are ready and mounted (if needed)
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#. the matching ``ceph-osd`` systemd unit will get started
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