mirror of https://github.com/ceph/ceph
325 lines
12 KiB
ReStructuredText
325 lines
12 KiB
ReStructuredText
.. _ceph-volume-lvm-prepare:
|
|
|
|
``prepare``
|
|
===========
|
|
This subcommand allows a :term:`filestore` or :term:`bluestore` setup. It is
|
|
recommended to pre-provision a logical volume before using it with
|
|
``ceph-volume lvm``.
|
|
|
|
Logical volumes are not altered except for adding extra metadata.
|
|
|
|
.. note:: This is part of a two step process to deploy an OSD. If looking for
|
|
a single-call way, please see :ref:`ceph-volume-lvm-create`
|
|
|
|
To help identify volumes, the process of preparing a volume (or volumes) to
|
|
work with Ceph, the tool will assign a few pieces of metadata information using
|
|
:term:`LVM tags`.
|
|
|
|
:term:`LVM tags` makes volumes easy to discover later, and help identify them as
|
|
part of a Ceph system, and what role they have (journal, filestore, bluestore,
|
|
etc...)
|
|
|
|
Although initially :term:`filestore` is supported (and supported by default)
|
|
the back end can be specified with:
|
|
|
|
|
|
* :ref:`--filestore <ceph-volume-lvm-prepare_filestore>`
|
|
* :ref:`--bluestore <ceph-volume-lvm-prepare_bluestore>`
|
|
|
|
.. _ceph-volume-lvm-prepare_filestore:
|
|
|
|
``filestore``
|
|
-------------
|
|
This is the OSD backend that allows preparation of logical volumes for
|
|
a :term:`filestore` objectstore OSD.
|
|
|
|
It can use a logical volume for the OSD data and a partitioned physical device
|
|
or logical volume for the journal. No special preparation is needed for these
|
|
volumes other than following the minimum size requirements for data and
|
|
journal.
|
|
|
|
The API call looks like::
|
|
|
|
ceph-volume lvm prepare --filestore --data volume_group/lv_name --journal journal
|
|
|
|
For enabling :ref:`encryption <ceph-volume-lvm-encryption>`, the ``--dmcrypt`` flag is required::
|
|
|
|
ceph-volume lvm prepare --filestore --dmcrypt --data volume_group/lv_name --journal journal
|
|
|
|
There is flexibility to use a raw device or partition as well for ``--data``
|
|
that will be converted to a logical volume. This is not ideal in all situations
|
|
since ``ceph-volume`` is just going to create a unique volume group and
|
|
a logical volume from that device.
|
|
|
|
When using logical volumes for ``--data``, the value *must* be a volume group
|
|
name and a logical volume name separated by a ``/``. Since logical volume names
|
|
are not enforced for uniqueness, this prevents using the wrong volume. The
|
|
``--journal`` can be either a logical volume *or* a partition.
|
|
|
|
When using a partition, it *must* contain a ``PARTUUID`` discoverable by
|
|
``blkid``, so that it can later be identified correctly regardless of the
|
|
device name (or path).
|
|
|
|
When using a partition, this is how it would look for ``/dev/sdc1``::
|
|
|
|
ceph-volume lvm prepare --filestore --data volume_group/lv_name --journal /dev/sdc1
|
|
|
|
For a logical volume, just like for ``--data``, a volume group and logical
|
|
volume name are required::
|
|
|
|
ceph-volume lvm prepare --filestore --data volume_group/lv_name --journal volume_group/journal_lv
|
|
|
|
A generated uuid is used to ask the cluster for a new OSD. These two pieces are
|
|
crucial for identifying an OSD and will later be used throughout the
|
|
:ref:`ceph-volume-lvm-activate` process.
|
|
|
|
The OSD data directory is created using the following convention::
|
|
|
|
/var/lib/ceph/osd/<cluster name>-<osd id>
|
|
|
|
At this point the data volume is mounted at this location, and the journal
|
|
volume is linked::
|
|
|
|
ln -s /path/to/journal /var/lib/ceph/osd/<cluster_name>-<osd-id>/journal
|
|
|
|
The monmap is fetched using the bootstrap key from the OSD::
|
|
|
|
/usr/bin/ceph --cluster ceph --name client.bootstrap-osd
|
|
--keyring /var/lib/ceph/bootstrap-osd/ceph.keyring
|
|
mon getmap -o /var/lib/ceph/osd/<cluster name>-<osd id>/activate.monmap
|
|
|
|
``ceph-osd`` will be called to populate the OSD directory, that is already
|
|
mounted, re-using all the pieces of information from the initial steps::
|
|
|
|
ceph-osd --cluster ceph --mkfs --mkkey -i <osd id> \
|
|
--monmap /var/lib/ceph/osd/<cluster name>-<osd id>/activate.monmap --osd-data \
|
|
/var/lib/ceph/osd/<cluster name>-<osd id> --osd-journal /var/lib/ceph/osd/<cluster name>-<osd id>/journal \
|
|
--osd-uuid <osd uuid> --keyring /var/lib/ceph/osd/<cluster name>-<osd id>/keyring \
|
|
--setuser ceph --setgroup ceph
|
|
|
|
|
|
.. _ceph-volume-lvm-partitions:
|
|
|
|
Partitioning
|
|
------------
|
|
``ceph-volume lvm`` does not currently create partitions from a whole device.
|
|
If using device partitions the only requirement is that they contain the
|
|
``PARTUUID`` and that it is discoverable by ``blkid``. Both ``fdisk`` and
|
|
``parted`` will create that automatically for a new partition.
|
|
|
|
For example, using a new, unformatted drive (``/dev/sdd`` in this case) we can
|
|
use ``parted`` to create a new partition. First we list the device
|
|
information::
|
|
|
|
$ parted --script /dev/sdd print
|
|
Model: VBOX HARDDISK (scsi)
|
|
Disk /dev/sdd: 11.5GB
|
|
Sector size (logical/physical): 512B/512B
|
|
Disk Flags:
|
|
|
|
This device is not even labeled yet, so we can use ``parted`` to create
|
|
a ``gpt`` label before we create a partition, and verify again with ``parted
|
|
print``::
|
|
|
|
$ parted --script /dev/sdd mklabel gpt
|
|
$ parted --script /dev/sdd print
|
|
Model: VBOX HARDDISK (scsi)
|
|
Disk /dev/sdd: 11.5GB
|
|
Sector size (logical/physical): 512B/512B
|
|
Partition Table: gpt
|
|
Disk Flags:
|
|
|
|
Now lets create a single partition, and verify later if ``blkid`` can find
|
|
a ``PARTUUID`` that is needed by ``ceph-volume``::
|
|
|
|
$ parted --script /dev/sdd mkpart primary 1 100%
|
|
$ blkid /dev/sdd1
|
|
/dev/sdd1: PARTLABEL="primary" PARTUUID="16399d72-1e1f-467d-96ee-6fe371a7d0d4"
|
|
|
|
|
|
.. _ceph-volume-lvm-existing-osds:
|
|
|
|
Existing OSDs
|
|
-------------
|
|
For existing clusters that want to use this new system and have OSDs that are
|
|
already running there are a few things to take into account:
|
|
|
|
.. warning:: this process will forcefully format the data device, destroying
|
|
existing data, if any.
|
|
|
|
* OSD paths should follow this convention::
|
|
|
|
/var/lib/ceph/osd/<cluster name>-<osd id>
|
|
|
|
* Preferably, no other mechanisms to mount the volume should exist, and should
|
|
be removed (like fstab mount points)
|
|
|
|
The one time process for an existing OSD, with an ID of 0 and using
|
|
a ``"ceph"`` cluster name would look like (the following command will **destroy
|
|
any data** in the OSD)::
|
|
|
|
ceph-volume lvm prepare --filestore --osd-id 0 --osd-fsid E3D291C1-E7BF-4984-9794-B60D9FA139CB
|
|
|
|
The command line tool will not contact the monitor to generate an OSD ID and
|
|
will format the LVM device in addition to storing the metadata on it so that it
|
|
can be started later (for detailed metadata description see
|
|
:ref:`ceph-volume-lvm-tags`).
|
|
|
|
|
|
.. _ceph-volume-lvm-prepare_bluestore:
|
|
|
|
``bluestore``
|
|
-------------
|
|
The :term:`bluestore` objectstore is the default for new OSDs. It offers a bit
|
|
more flexibility for devices. Bluestore supports the following configurations:
|
|
|
|
* A block device, a block.wal, and a block.db device
|
|
* A block device and a block.wal device
|
|
* A block device and a block.db device
|
|
* A single block device
|
|
|
|
It can accept a whole device (or partition), or a logical volume for ``block``.
|
|
If a physical device is provided it will then be turned into a logical volume.
|
|
This allows a simpler approach at using LVM but at the cost of flexibility:
|
|
there are no options or configurations to change how the LV is created.
|
|
|
|
The ``block`` is specified with the ``--data`` flag, and in its simplest use
|
|
case it looks like::
|
|
|
|
ceph-volume lvm prepare --bluestore --data vg/lv
|
|
|
|
A raw device can be specified in the same way::
|
|
|
|
ceph-volume lvm prepare --bluestore --data /path/to/device
|
|
|
|
For enabling :ref:`encryption <ceph-volume-lvm-encryption>`, the ``--dmcrypt`` flag is required::
|
|
|
|
ceph-volume lvm prepare --bluestore --dmcrypt --data vg/lv
|
|
|
|
If a ``block.db`` or a ``block.wal`` is needed (they are optional for
|
|
bluestore) they can be specified with ``--block.db`` and ``--block.wal``
|
|
accordingly. These can be a physical device (they **must** be a partition) or
|
|
a logical volume.
|
|
|
|
For both ``block.db`` and ``block.wal`` partitions aren't made logical volumes
|
|
because they can be used as-is. Logical Volumes are also allowed.
|
|
|
|
While creating the OSD directory, the process will use a ``tmpfs`` mount to
|
|
place all the files needed for the OSD. These files are initially created by
|
|
``ceph-osd --mkfs`` and are fully ephemeral.
|
|
|
|
A symlink is always created for the ``block`` device, and optionally for
|
|
``block.db`` and ``block.wal``. For a cluster with a default name, and an OSD
|
|
id of 0, the directory could look like::
|
|
|
|
# ls -l /var/lib/ceph/osd/ceph-0
|
|
lrwxrwxrwx. 1 ceph ceph 93 Oct 20 13:05 block -> /dev/ceph-be2b6fbd-bcf2-4c51-b35d-a35a162a02f0/osd-block-25cf0a05-2bc6-44ef-9137-79d65bd7ad62
|
|
lrwxrwxrwx. 1 ceph ceph 93 Oct 20 13:05 block.db -> /dev/sda1
|
|
lrwxrwxrwx. 1 ceph ceph 93 Oct 20 13:05 block.wal -> /dev/ceph/osd-wal-0
|
|
-rw-------. 1 ceph ceph 37 Oct 20 13:05 ceph_fsid
|
|
-rw-------. 1 ceph ceph 37 Oct 20 13:05 fsid
|
|
-rw-------. 1 ceph ceph 55 Oct 20 13:05 keyring
|
|
-rw-------. 1 ceph ceph 6 Oct 20 13:05 ready
|
|
-rw-------. 1 ceph ceph 10 Oct 20 13:05 type
|
|
-rw-------. 1 ceph ceph 2 Oct 20 13:05 whoami
|
|
|
|
In the above case, a device was used for ``block`` so ``ceph-volume`` create
|
|
a volume group and a logical volume using the following convention:
|
|
|
|
* volume group name: ``ceph-{cluster fsid}`` or if the vg exists already
|
|
``ceph-{random uuid}``
|
|
|
|
* logical volume name: ``osd-block-{osd_fsid}``
|
|
|
|
|
|
Crush device class
|
|
------------------
|
|
|
|
To set the crush device class for the OSD, use the ``--crush-device-class`` flag. This will
|
|
work for both bluestore and filestore OSDs::
|
|
|
|
ceph-volume lvm prepare --bluestore --data vg/lv --crush-device-class foo
|
|
|
|
|
|
.. _ceph-volume-lvm-multipath:
|
|
|
|
``multipath`` support
|
|
---------------------
|
|
Devices that come from ``multipath`` are not supported as-is. The tool will
|
|
refuse to consume a raw multipath device and will report a message like::
|
|
|
|
--> RuntimeError: Cannot use device (/dev/mapper/<name>). A vg/lv path or an existing device is needed
|
|
|
|
The reason for not supporting multipath is that depending on the type of the
|
|
multipath setup, if using an active/passive array as the underlying physical
|
|
devices, filters are required in ``lvm.conf`` to exclude the disks that are part of
|
|
those underlying devices.
|
|
|
|
It is unfeasible for ceph-volume to understand what type of configuration is
|
|
needed for LVM to be able to work in various different multipath scenarios. The
|
|
functionality to create the LV for you is merely a (naive) convenience,
|
|
anything that involves different settings or configuration must be provided by
|
|
a config management system which can then provide VGs and LVs for ceph-volume
|
|
to consume.
|
|
|
|
This situation will only arise when trying to use the ceph-volume functionality
|
|
that creates a volume group and logical volume from a device. If a multipath
|
|
device is already a logical volume it *should* work, given that the LVM
|
|
configuration is done correctly to avoid issues.
|
|
|
|
|
|
Storing metadata
|
|
----------------
|
|
The following tags will get applied as part of the preparation process
|
|
regardless of the type of volume (journal or data) or OSD objectstore:
|
|
|
|
* ``cluster_fsid``
|
|
* ``encrypted``
|
|
* ``osd_fsid``
|
|
* ``osd_id``
|
|
* ``crush_device_class``
|
|
|
|
For :term:`filestore` these tags will be added:
|
|
|
|
* ``journal_device``
|
|
* ``journal_uuid``
|
|
|
|
For :term:`bluestore` these tags will be added:
|
|
|
|
* ``block_device``
|
|
* ``block_uuid``
|
|
* ``db_device``
|
|
* ``db_uuid``
|
|
* ``wal_device``
|
|
* ``wal_uuid``
|
|
|
|
.. note:: For the complete lvm tag conventions see :ref:`ceph-volume-lvm-tag-api`
|
|
|
|
|
|
Summary
|
|
-------
|
|
To recap the ``prepare`` process for :term:`bluestore`:
|
|
|
|
#. Accept a logical volume for block or a raw device (that will get converted
|
|
to an lv)
|
|
#. Accept partitions or logical volumes for ``block.wal`` or ``block.db``
|
|
#. Generate a UUID for the OSD
|
|
#. Ask the monitor get an OSD ID reusing the generated UUID
|
|
#. OSD data directory is created on a tmpfs mount.
|
|
#. ``block``, ``block.wal``, and ``block.db`` are symlinked if defined.
|
|
#. monmap is fetched for activation
|
|
#. Data directory is populated by ``ceph-osd``
|
|
#. Logical Volumes are assigned all the Ceph metadata using lvm tags
|
|
|
|
|
|
And the ``prepare`` process for :term:`filestore`:
|
|
|
|
#. Accept only logical volumes for data and journal (both required)
|
|
#. Generate a UUID for the OSD
|
|
#. Ask the monitor get an OSD ID reusing the generated UUID
|
|
#. OSD data directory is created and data volume mounted
|
|
#. Journal is symlinked from data volume to journal location
|
|
#. monmap is fetched for activation
|
|
#. devices is mounted and data directory is populated by ``ceph-osd``
|
|
#. data and journal volumes are assigned all the Ceph metadata using lvm tags
|