mirror of https://github.com/ceph/ceph
302 lines
10 KiB
ReStructuredText
302 lines
10 KiB
ReStructuredText
======================
|
|
Adding/Removing OSDs
|
|
======================
|
|
|
|
When you have a cluster up and running, you may add OSDs or remove OSDs
|
|
from the cluster at runtime.
|
|
|
|
Adding OSDs
|
|
===========
|
|
|
|
When you want to expand a cluster, you may add an OSD at runtime. With Ceph, an
|
|
OSD is generally one Ceph ``ceph-osd`` daemon for one storage drive within a
|
|
host machine. If your host has multiple storage drives, you may map one
|
|
``ceph-osd`` daemon for each drive.
|
|
|
|
Generally, it's a good idea to check the capacity of your cluster to see if you
|
|
are reaching the upper end of its capacity. As your cluster reaches its ``near
|
|
full`` ratio, you should add one or more OSDs to expand your cluster's capacity.
|
|
|
|
.. warning:: Do not let your cluster reach its ``full ratio`` before
|
|
adding an OSD. OSD failures that occur after the cluster reaches
|
|
its ``near full`` ratio may cause the cluster to exceed its
|
|
``full ratio``.
|
|
|
|
Deploy your Hardware
|
|
--------------------
|
|
|
|
If you are adding a new host when adding a new OSD, see `Hardware
|
|
Recommendations`_ for details on minimum recommendations for OSD hardware. To
|
|
add an OSD host to your cluster, first make sure you have an up-to-date version
|
|
of Linux installed, and you have made some initial preparations for your
|
|
storage drives. See `Filesystem Recommendations`_ for details.
|
|
|
|
Add your OSD host to a rack in your cluster, connect it to the network
|
|
and ensure that it has network connectivity. See the `Network Configuration
|
|
Reference`_ for details.
|
|
|
|
.. _Hardware Recommendations: ../../../install/hardware-recommendations
|
|
.. _Filesystem Recommendations: ../../configuration/filesystem-recommendations
|
|
.. _Network Configuration Reference: ../../configuration/network-config-ref
|
|
|
|
Install the Required Software
|
|
-----------------------------
|
|
|
|
For manually deployed clusters, you must install Ceph packages
|
|
manually. See `Installing Ceph (Manual)`_ for details.
|
|
You should configure SSH to a user with password-less authentication
|
|
and root permissions.
|
|
|
|
.. _Installing Ceph (Manual): ../../../install
|
|
|
|
|
|
Adding an OSD (Manual)
|
|
----------------------
|
|
|
|
This procedure sets up a ``ceph-osd`` daemon, configures it to use one drive,
|
|
and configures the cluster to distribute data to the OSD. If your host has
|
|
multiple drives, you may add an OSD for each drive by repeating this procedure.
|
|
|
|
To add an OSD, create a data directory for it, mount a drive to that directory,
|
|
add the OSD to the cluster, and then add it to the CRUSH map.
|
|
|
|
When you add the OSD to the CRUSH map, consider the weight you give to the new
|
|
OSD. Hard drive capacity grows 40% per year, so newer OSD hosts may have larger
|
|
hard drives than older hosts in the cluster (i.e., they may have greater
|
|
weight).
|
|
|
|
.. tip:: Ceph prefers uniform hardware across pools. If you are adding drives
|
|
of dissimilar size, you can adjust their weights. However, for best
|
|
performance, consider a CRUSH hierarchy with drives of the same type/size.
|
|
|
|
#. Create the OSD. If no UUID is given, it will be set automatically when the
|
|
OSD starts up. The following command will output the OSD number, which you
|
|
will need for subsequent steps. ::
|
|
|
|
ceph osd create [{uuid}]
|
|
|
|
|
|
#. Create the default directory on your new OSD. ::
|
|
|
|
ssh {new-osd-host}
|
|
sudo mkdir /var/lib/ceph/osd/ceph-{osd-number}
|
|
|
|
|
|
#. If the OSD is for a drive other than the OS drive, prepare it
|
|
for use with Ceph, and mount it to the directory you just created::
|
|
|
|
ssh {new-osd-host}
|
|
sudo mkfs -t {fstype} /dev/{drive}
|
|
sudo mount -o user_xattr /dev/{hdd} /var/lib/ceph/osd/ceph-{osd-number}
|
|
|
|
|
|
#. Initialize the OSD data directory. ::
|
|
|
|
ssh {new-osd-host}
|
|
ceph-osd -i {osd-num} --mkfs --mkkey
|
|
|
|
The directory must be empty before you can run ``ceph-osd``.
|
|
|
|
#. Register the OSD authentication key. The value of ``ceph`` for
|
|
``ceph-{osd-num}`` in the path is the ``$cluster-$id``. If your
|
|
cluster name differs from ``ceph``, use your cluster name instead.::
|
|
|
|
ceph auth add osd.{osd-num} osd 'allow *' mon 'allow rwx' -i /var/lib/ceph/osd/ceph-{osd-num}/keyring
|
|
|
|
|
|
#. Add the OSD to the CRUSH map so that the OSD can begin receiving data. The
|
|
``ceph osd crush add`` command allows you to add OSDs to the CRUSH hierarchy
|
|
wherever you wish. If you specify at least one bucket, the command
|
|
will place the OSD into the most specific bucket you specify, *and* it will
|
|
move that bucket underneath any other buckets you specify. **Important:** If
|
|
you specify only the root bucket, the command will attach the OSD directly
|
|
to the root, but CRUSH rules expect OSDs to be inside of hosts.
|
|
|
|
For Argonaut (v 0.48), execute the following::
|
|
|
|
ceph osd crush add {id} {name} {weight} [{bucket-type}={bucket-name} ...]
|
|
|
|
For Bobtail (v 0.56) and later releases, execute the following::
|
|
|
|
ceph osd crush add {id-or-name} {weight} [{bucket-type}={bucket-name} ...]
|
|
|
|
You may also decompile the CRUSH map, add the OSD to the device list, add the
|
|
host as a bucket (if it's not already in the CRUSH map), add the device as an
|
|
item in the host, assign it a weight, recompile it and set it. See
|
|
`Add/Move an OSD`_ for details.
|
|
|
|
|
|
.. topic:: Argonaut (v0.48) Best Practices
|
|
|
|
To limit impact on user I/O performance, add an OSD to the CRUSH map
|
|
with an initial weight of ``0``. Then, ramp up the CRUSH weight a
|
|
little bit at a time. For example, to ramp by increments of ``0.2``,
|
|
start with::
|
|
|
|
ceph osd crush reweight {osd-id} .2
|
|
|
|
and allow migration to complete before reweighting to ``0.4``,
|
|
``0.6``, and so on until the desired CRUSH weight is reached.
|
|
|
|
To limit the impact of OSD failures, you can set::
|
|
|
|
mon osd down out interval = 0
|
|
|
|
which prevents down OSDs from automatically being marked out, and then
|
|
ramp them down manually with::
|
|
|
|
ceph osd reweight {osd-num} .8
|
|
|
|
Again, wait for the cluster to finish migrating data, and then adjust
|
|
the weight further until you reach a weight of 0. Note that this
|
|
problem prevents the cluster to automatically re-replicate data after
|
|
a failure, so please ensure that sufficient monitoring is in place for
|
|
an administrator to intervene promptly.
|
|
|
|
Note that this practice will no longer be necessary in Bobtail and
|
|
subsequent releases.
|
|
|
|
|
|
Starting the OSD
|
|
----------------
|
|
|
|
After you add an OSD to Ceph, the OSD is in your configuration. However,
|
|
it is not yet running. The OSD is ``down`` and ``in``. You must start
|
|
your new OSD before it can begin receiving data. You may use
|
|
``service ceph`` from your admin host or start the OSD from its host
|
|
machine.
|
|
|
|
For Debian/Ubuntu use Upstart. ::
|
|
|
|
sudo start ceph-osd id={osd-num}
|
|
|
|
For CentOS/RHEL, use sysvinit. ::
|
|
|
|
sudo /etc/init.d/ceph start osd.{osd-num}
|
|
|
|
|
|
Once you start your OSD, it is ``up`` and ``in``.
|
|
|
|
|
|
Observe the Data Migration
|
|
--------------------------
|
|
|
|
Once you have added your new OSD to the CRUSH map, Ceph will begin rebalancing
|
|
the server by migrating placement groups to your new OSD. You can observe this
|
|
process with the `ceph`_ tool. ::
|
|
|
|
ceph -w
|
|
|
|
You should see the placement group states change from ``active+clean`` to
|
|
``active, some degraded objects``, and finally ``active+clean`` when migration
|
|
completes. (Control-c to exit.)
|
|
|
|
|
|
.. _Add/Move an OSD: ../crush-map#addosd
|
|
.. _ceph: ../monitoring
|
|
|
|
|
|
|
|
Removing OSDs (Manual)
|
|
======================
|
|
|
|
When you want to reduce the size of a cluster or replace hardware, you may
|
|
remove an OSD at runtime. With Ceph, an OSD is generally one Ceph ``ceph-osd``
|
|
daemon for one storage drive within a host machine. If your host has multiple
|
|
storage drives, you may need to remove one ``ceph-osd`` daemon for each drive.
|
|
Generally, it's a good idea to check the capacity of your cluster to see if you
|
|
are reaching the upper end of its capacity. Ensure that when you remove an OSD
|
|
that your cluster is not at its ``near full`` ratio.
|
|
|
|
.. warning:: Do not let your cluster reach its ``full ratio`` when
|
|
removing an OSD. Removing OSDs could cause the cluster to reach
|
|
or exceed its ``full ratio``.
|
|
|
|
|
|
Take the OSD ``out`` of the Cluster
|
|
-----------------------------------
|
|
|
|
Before you remove an OSD, it is usually ``up`` and ``in``. You need to take it
|
|
out of the cluster so that Ceph can begin rebalancing and copying its data to
|
|
other OSDs. ::
|
|
|
|
ceph osd out {osd-num}
|
|
|
|
|
|
Observe the Data Migration
|
|
--------------------------
|
|
|
|
Once you have taken your OSD ``out`` of the cluster, Ceph will begin
|
|
rebalancing the cluster by migrating placement groups out of the OSD you
|
|
removed. You can observe this process with the `ceph`_ tool. ::
|
|
|
|
ceph -w
|
|
|
|
You should see the placement group states change from ``active+clean`` to
|
|
``active, some degraded objects``, and finally ``active+clean`` when migration
|
|
completes. (Control-c to exit.)
|
|
|
|
|
|
Stopping the OSD
|
|
----------------
|
|
|
|
After you take an OSD out of the cluster, it may still be running.
|
|
That is, the OSD may be ``up`` and ``out``. You must stop
|
|
your OSD before you remove it from the configuration. ::
|
|
|
|
ssh {osd-host}
|
|
sudo /etc/init.d/ceph stop osd.{osd-num}
|
|
|
|
Once you stop your OSD, it is ``down``.
|
|
|
|
|
|
Removing the OSD
|
|
----------------
|
|
|
|
This procedure removes an OSD from a cluster map, removes its authentication
|
|
key, removes the OSD from the OSD map, and removes the OSD from the
|
|
``ceph.conf`` file. If your host has multiple drives, you may need to remove an
|
|
OSD for each drive by repeating this procedure.
|
|
|
|
|
|
#. Remove the OSD from the CRUSH map so that it no longer receives data. You may
|
|
also decompile the CRUSH map, remove the OSD from the device list, remove the
|
|
device as an item in the host bucket or remove the host bucket (if it's in the
|
|
CRUSH map and you intend to remove the host), recompile the map and set it.
|
|
See `Remove an OSD`_ for details. ::
|
|
|
|
ceph osd crush remove {name}
|
|
|
|
#. Remove the OSD authentication key. ::
|
|
|
|
ceph auth del osd.{osd-num}
|
|
|
|
The value of ``ceph`` for ``ceph-{osd-num}`` in the path is the ``$cluster-$id``.
|
|
If your cluster name differs from ``ceph``, use your cluster name instead.
|
|
|
|
#. Remove the OSD. ::
|
|
|
|
ceph osd rm {osd-num}
|
|
#for example
|
|
ceph osd rm 1
|
|
|
|
#. Navigate to the host where you keep the master copy of the cluster's
|
|
``ceph.conf`` file. ::
|
|
|
|
ssh {admin-host}
|
|
cd /etc/ceph
|
|
vim ceph.conf
|
|
|
|
#. Remove the OSD entry from your ``ceph.conf`` file (if it exists). ::
|
|
|
|
[osd.1]
|
|
host = {hostname}
|
|
|
|
#. From the host where you keep the master copy of the cluster's ``ceph.conf`` file,
|
|
copy the updated ``ceph.conf`` file to the ``/etc/ceph`` directory of other
|
|
hosts in your cluster.
|
|
|
|
|
|
|
|
.. _Remove an OSD: ../crush-map#removeosd
|