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Merge pull request #16741 from liewegas/wip-more-doc-links
doc/release-notes: fix links, formatting; add crush device class docs Reviewed-by: Kefu Chai <kchai@redhat.com>
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Kefu Chai
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@ -206,6 +206,43 @@ You can view the contents of the rules with::
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ceph osd crush rule dump
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Device classes
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--------------
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Each device can optionally have a *class* associated with it. By
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default, OSDs automatically set their class on startup to either
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`hdd`, `ssd`, or `nvme` based on the type of device they are backed
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by.
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The device class for one or more OSDs can be explicitly set with::
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ceph osd crush set-device-class <class> <osd-name> [...]
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Once a device class is set, it cannot be changed to another class
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until the old class is unset with::
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ceph osd crush rm-device-class <osd-name> [...]
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This allows administrators to set device classes without the class
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being changed on OSD restart or by some other script.
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A placement rule that targets a specific device class can be created with::
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ceph osd crush rule create-replicated <rule-name> <root> <failure-domain> <class>
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A pool can then be changed to use the new rule with::
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ceph osd pool set <pool-name> crush_rule <rule-name>
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Device classes are implemented by creating a "shadow" CRUSH hierarchy
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for each device class in use that contains only devices of that class.
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Rules can then distributed data over the shadow hierarchy. One nice
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thing about this approach is that it is fully backward compatible with
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old Ceph clients. You can view the CRUSH hierarchy with shadow items
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with::
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ceph osd crush tree --show-shadow
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Weights sets
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------------
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@ -18,62 +18,60 @@ Major Changes from Kraken
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- *General*:
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* Ceph now has a simple, built-in web-based dashboard for monitoring
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cluster status. See :doc:`/mgr/dashboard/`.
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* Ceph now has a simple, `built-in web-based dashboard
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<../mgr/dashboard>`_ for monitoring cluster status.
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- *RADOS*:
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* *BlueStore*:
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- The new *BlueStore* backend for *ceph-osd* is now stable and the new
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default for newly created OSDs. BlueStore manages data stored by each OSD
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by directly managing the physical HDDs or SSDs without the use of an
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intervening file system like XFS. This provides greater performance
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and features. FIXME DOCS
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- BlueStore supports *full data and metadata checksums* of all
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data stored by Ceph.
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- BlueStore supports inline compression using zlib, snappy, or LZ4. (Ceph
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also supports zstd for RGW compression but zstd is not recommended for
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BlueStore for performance reasons.) FIXME DOCS
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* *Erasure coded* pools now have full support for *overwrites*,
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allowing them to be used with RBD and CephFS. See :doc:`/rados/operations/erasure-code/#erasure-coding-with-overwrites`.
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* *ceph-mgr*:
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- There is a new daemon, *ceph-mgr*, which is a required part of any
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Ceph deployment. Although IO can continue when *ceph-mgr* is
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down, metrics will not refresh and some metrics-related calls
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(e.g., ``ceph df``) may block. We recommend deploying several instances of
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*ceph-mgr* for reliability. See the notes on `Upgrading`_ below.
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- The *ceph-mgr* daemon includes a REST-based management API. The
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API is still experimental and somewhat limited but will form the basis
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for API-based management of Ceph going forward. See :doc:`/mgr/restful`.
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- *ceph-mgr* also includes a Prometheus exporter plugin, which can
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provide Ceph perfcounters to Prometheus. See :doc:`/mgr/prometheus`.
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* The new *BlueStore* backend for *ceph-osd* is now stable and the new
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default for newly created OSDs. BlueStore manages data stored by each OSD
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by directly managing the physical HDDs or SSDs without the use of an
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intervening file system like XFS. This provides greater performance
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and features. FIXME DOCS
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* BlueStore supports *full data and metadata checksums* of all
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data stored by Ceph.
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* BlueStore supports inline compression using zlib, snappy, or LZ4. (Ceph
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also supports zstd for RGW compression but zstd is not recommended for
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BlueStore for performance reasons.) FIXME DOCS
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* *Erasure coded* pools now have `full support for overwrites <../rados/operations/erasure-code/#erasure-coding-with-overwrites>`_,
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allowing them to be used with RBD and CephFS.
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* There is a new daemon, *ceph-mgr*, which is a required part of any
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Ceph deployment. Although IO can continue when *ceph-mgr* is
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down, metrics will not refresh and some metrics-related calls
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(e.g., ``ceph df``) may block. We recommend deploying several instances of
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*ceph-mgr* for reliability. See the notes on `Upgrading`_ below.
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* The *ceph-mgr* daemon includes a `REST-based management API
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<../mgr/restful>`_. The API is still experimental and somewhat
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limited but will form the basis for API-based management of Ceph
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going forward.
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* *ceph-mgr* also includes a `Prometheus exporter <../mgr/prometheus>`_
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plugin, which can provide Ceph perfcounters to Prometheus.
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* The overall *scalability* of the cluster has improved. We have
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successfully tested clusters with up to 10,000 OSDs.
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* Each OSD can now have a *device class* associated with it (e.g.,
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`hdd` or `ssd`), allowing CRUSH rules to trivially map data to a
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subset of devices in the system. Manually writing CRUSH rules or
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manual editing of the CRUSH is normally not required. See
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:doc:`/rados/operations/crush-map/#crush-structure`.
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* Each OSD can now have a `device class
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<../rados/operations/crush-map/#device-classes>`_ associated with
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it (e.g., `hdd` or `ssd`), allowing CRUSH rules to trivially map
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data to a subset of devices in the system. Manually writing CRUSH
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rules or manual editing of the CRUSH is normally not required.
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* You can now *optimize CRUSH weights* to maintain a *near-perfect
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distribution of data* across OSDs. FIXME DOCS
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* There is also a new `upmap` exception mechanism that allows
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individual PGs to be moved around to achieve a *perfect
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distribution* (this requires luminous clients). See
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:doc:`/rados/operations/upmap`.
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* There is also a new `upmap <../rados/operations/upmap>`_ exception
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mechanism that allows individual PGs to be moved around to achieve
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a *perfect distribution* (this requires luminous clients).
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* Each OSD now adjusts its default configuration based on whether the
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backing device is an HDD or SSD. Manual tuning generally not required.
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* The prototype `mClock QoS queueing algorithm </rados/configuration/osd-config-ref/#qos-based-on-mclock>` is now available.
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* The prototype `mClock QoS queueing algorithm
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<../rados/configuration/osd-config-ref/#qos-based-on-mclock>`_ is now
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available.
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* There is now a *backoff* mechanism that prevents OSDs from being
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overloaded by requests to objects or PGs that are not currently able to
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process IO.
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* There is a simplified OSD replacement process that is more robust (see :doc:`/rados/operations/add-or-rm-osds/#replacing-an-osd`).
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* There is a simplified `OSD replacement process
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<../rados/operations/add-or-rm-osds/#replacing-an-osd>`_ that is more
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robust.
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* You can query the supported features and (apparent) releases of
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all connected daemons and clients with `ceph features </man/8/ceph#features>`_.
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all connected daemons and clients with `ceph features
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<../man/8/ceph#features>`_.
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* You can configure the oldest Ceph client version you wish to allow to
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connect to the cluster via ``ceph osd set-require-min-compat-client`` and
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Ceph will prevent you from enabling features that will break compatibility
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@ -148,7 +146,8 @@ Major Changes from Kraken
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- *Miscellaneous*:
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* Release packages are now being built for *Debian Stretch*. The
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* Release packages are now being built for *Debian Stretch*. Note
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that QA is limited to CentOS and Ubuntu (xenial and trusty). The
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distributions we build for now includes:
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- CentOS 7 (x86_64 and aarch64)
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@ -157,8 +156,6 @@ Major Changes from Kraken
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- Ubuntu 16.04 Xenial (x86_64 and aarch64)
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- Ubuntu 14.04 Trusty (x86_64)
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Note that QA is limited to CentOS and Ubuntu (xenial and trusty).
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* *CLI changes*:
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- The ``ceph -s`` or ``ceph status`` command has a fresh look.
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