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Signed-off-by: Kefu Chai <kchai@redhat.com>
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ReStructuredText
409 lines
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=====================================
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Configuring Monitor/OSD Interaction
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=====================================
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.. index:: heartbeat
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After you have completed your initial Ceph configuration, you may deploy and run
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Ceph. When you execute a command such as ``ceph health`` or ``ceph -s``, the
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:term:`Ceph Monitor` reports on the current state of the :term:`Ceph Storage
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Cluster`. The Ceph Monitor knows about the Ceph Storage Cluster by requiring
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reports from each :term:`Ceph OSD Daemon`, and by receiving reports from Ceph
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OSD Daemons about the status of their neighboring Ceph OSD Daemons. If the Ceph
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Monitor doesn't receive reports, or if it receives reports of changes in the
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Ceph Storage Cluster, the Ceph Monitor updates the status of the :term:`Ceph
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Cluster Map`.
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Ceph provides reasonable default settings for Ceph Monitor/Ceph OSD Daemon
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interaction. However, you may override the defaults. The following sections
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describe how Ceph Monitors and Ceph OSD Daemons interact for the purposes of
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monitoring the Ceph Storage Cluster.
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.. index:: heartbeat interval
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OSDs Check Heartbeats
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=====================
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Each Ceph OSD Daemon checks the heartbeat of other Ceph OSD Daemons every 6
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seconds. You can change the heartbeat interval by adding an ``osd heartbeat
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interval`` setting under the ``[osd]`` section of your Ceph configuration file,
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or by setting the value at runtime. If a neighboring Ceph OSD Daemon doesn't
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show a heartbeat within a 20 second grace period, the Ceph OSD Daemon may
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consider the neighboring Ceph OSD Daemon ``down`` and report it back to a Ceph
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Monitor, which will update the Ceph Cluster Map. You may change this grace
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period by adding an ``osd heartbeat grace`` setting under the ``[mon]``
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and ``[osd]`` or ``[global]`` section of your Ceph configuration file,
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or by setting the value at runtime.
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.. ditaa:: +---------+ +---------+
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| OSD 1 | | OSD 2 |
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+---------+ +---------+
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| |
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|----+ Heartbeat |
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| | Interval |
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|<---+ Exceeded |
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| |
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| Check |
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| Heartbeat |
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|------------------->|
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|<-------------------|
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| Heart Beating |
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|----+ Heartbeat |
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| | Interval |
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|<---+ Exceeded |
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| Check |
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| Heartbeat |
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|------------------->|
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|----+ Grace |
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| | Period |
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|<---+ Exceeded |
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|----+ Mark |
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| | OSD 2 |
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|<---+ Down |
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.. index:: OSD down report
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OSDs Report Down OSDs
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=====================
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By default, two Ceph OSD Daemons from different hosts must report to the Ceph
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Monitors that another Ceph OSD Daemon is ``down`` before the Ceph Monitors
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acknowledge that the reported Ceph OSD Daemon is ``down``. But there is chance
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that all the OSDs reporting the failure are hosted in a rack with a bad switch
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which has trouble connecting to another OSD. To avoid this sort of false alarm,
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we consider the peers reporting a failure a proxy for a potential "subcluster"
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over the overall cluster that is similarly laggy. This is clearly not true in
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all cases, but will sometimes help us localize the grace correction to a subset
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of the system that is unhappy. ``mon osd reporter subtree level`` is used to
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group the peers into the "subcluster" by their common ancestor type in CRUSH
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map. By default, only two reports from different subtree are required to report
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another Ceph OSD Daemon ``down``. You can change the number of reporters from
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unique subtrees and the common ancestor type required to report a Ceph OSD
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Daemon ``down`` to a Ceph Monitor by adding an ``mon osd min down reporters``
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and ``mon osd reporter subtree level`` settings under the ``[mon]`` section of
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your Ceph configuration file, or by setting the value at runtime.
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.. ditaa:: +---------+ +---------+ +---------+
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| OSD 1 | | OSD 2 | | Monitor |
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+---------+ +---------+ +---------+
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| | |
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| OSD 3 Is Down | |
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|---------------+--------------->|
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| | |
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| | OSD 3 Is Down |
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| |--------------->|
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| | |
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| | |
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| | |---------+ Mark
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| | | | OSD 3
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| | |<--------+ Down
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.. index:: peering failure
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OSDs Report Peering Failure
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===========================
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If a Ceph OSD Daemon cannot peer with any of the Ceph OSD Daemons defined in its
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Ceph configuration file (or the cluster map), it will ping a Ceph Monitor for
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the most recent copy of the cluster map every 30 seconds. You can change the
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Ceph Monitor heartbeat interval by adding an ``osd mon heartbeat interval``
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setting under the ``[osd]`` section of your Ceph configuration file, or by
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setting the value at runtime.
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.. ditaa:: +---------+ +---------+ +-------+ +---------+
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| OSD 1 | | OSD 2 | | OSD 3 | | Monitor |
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+---------+ +---------+ +-------+ +---------+
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| | | |
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| Request To | | |
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| Peer | | |
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|-------------->| | |
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|<--------------| | |
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| Peering | |
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| Request To | |
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| Peer | |
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|----------------------------->| |
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|----+ OSD Monitor |
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| | Heartbeat |
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|<---+ Interval Exceeded |
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| Failed to Peer with OSD 3 |
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|-------------------------------------------->|
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|<--------------------------------------------|
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| Receive New Cluster Map |
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.. index:: OSD status
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OSDs Report Their Status
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========================
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If an Ceph OSD Daemon doesn't report to a Ceph Monitor, the Ceph Monitor will
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consider the Ceph OSD Daemon ``down`` after the ``mon osd report timeout``
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elapses. A Ceph OSD Daemon sends a report to a Ceph Monitor when a reportable
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event such as a failure, a change in placement group stats, a change in
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``up_thru`` or when it boots within 5 seconds. You can change the Ceph OSD
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Daemon minimum report interval by adding an ``osd mon report interval min``
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setting under the ``[osd]`` section of your Ceph configuration file, or by
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setting the value at runtime. A Ceph OSD Daemon sends a report to a Ceph
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Monitor every 120 seconds irrespective of whether any notable changes occur.
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You can change the Ceph Monitor report interval by adding an ``osd mon report
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interval max`` setting under the ``[osd]`` section of your Ceph configuration
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file, or by setting the value at runtime.
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.. ditaa:: +---------+ +---------+
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| OSD 1 | | Monitor |
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+---------+ +---------+
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|----+ Report Min |
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| | Interval |
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|<---+ Exceeded |
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|----+ Reportable |
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| | Event |
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|<---+ Occurs |
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| Report To |
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| Monitor |
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|------------------->|
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|----+ Report Max |
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| | Interval |
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|<---+ Exceeded |
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| Report To |
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| Monitor |
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|------------------->|
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|----+ Monitor |
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| | Fails |
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|<---+ |
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+----+ Monitor OSD
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| | Report Timeout
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|<---+ Exceeded
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+----+ Mark
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| | OSD 1
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|<---+ Down
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Configuration Settings
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======================
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When modifying heartbeat settings, you should include them in the ``[global]``
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section of your configuration file.
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.. index:: monitor heartbeat
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Monitor Settings
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----------------
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``mon osd min up ratio``
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:Description: The minimum ratio of ``up`` Ceph OSD Daemons before Ceph will
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mark Ceph OSD Daemons ``down``.
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:Type: Double
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:Default: ``.3``
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``mon osd min in ratio``
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:Description: The minimum ratio of ``in`` Ceph OSD Daemons before Ceph will
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mark Ceph OSD Daemons ``out``.
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:Type: Double
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:Default: ``.75``
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``mon osd laggy halflife``
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:Description: The number of seconds laggy estimates will decay.
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:Type: Integer
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:Default: ``60*60``
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``mon osd laggy weight``
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:Description: The weight for new samples in laggy estimation decay.
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:Type: Double
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:Default: ``0.3``
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``mon osd laggy max interval``
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:Description: Maximum value of ``laggy_interval`` in laggy estimations (in seconds).
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Monitor uses an adaptive approach to evaluate the ``laggy_interval`` of
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a certain OSD. This value will be used to calculate the grace time for
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that OSD.
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:Type: Integer
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:Default: 300
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``mon osd adjust heartbeat grace``
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:Description: If set to ``true``, Ceph will scale based on laggy estimations.
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:Type: Boolean
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:Default: ``true``
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``mon osd adjust down out interval``
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:Description: If set to ``true``, Ceph will scaled based on laggy estimations.
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:Type: Boolean
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:Default: ``true``
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``mon osd auto mark in``
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:Description: Ceph will mark any booting Ceph OSD Daemons as ``in``
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the Ceph Storage Cluster.
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:Type: Boolean
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:Default: ``false``
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``mon osd auto mark auto out in``
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:Description: Ceph will mark booting Ceph OSD Daemons auto marked ``out``
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of the Ceph Storage Cluster as ``in`` the cluster.
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:Type: Boolean
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:Default: ``true``
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``mon osd auto mark new in``
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:Description: Ceph will mark booting new Ceph OSD Daemons as ``in`` the
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Ceph Storage Cluster.
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:Type: Boolean
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:Default: ``true``
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``mon osd down out interval``
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:Description: The number of seconds Ceph waits before marking a Ceph OSD Daemon
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``down`` and ``out`` if it doesn't respond.
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:Type: 32-bit Integer
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:Default: ``600``
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``mon osd down out subtree limit``
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:Description: The smallest :term:`CRUSH` unit type that Ceph will **not**
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automatically mark out. For instance, if set to ``host`` and if
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all OSDs of a host are down, Ceph will not automatically mark out
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these OSDs.
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:Type: String
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:Default: ``rack``
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``mon osd report timeout``
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:Description: The grace period in seconds before declaring
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unresponsive Ceph OSD Daemons ``down``.
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:Type: 32-bit Integer
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:Default: ``900``
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``mon osd min down reporters``
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:Description: The minimum number of Ceph OSD Daemons required to report a
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``down`` Ceph OSD Daemon.
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:Type: 32-bit Integer
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:Default: ``2``
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``mon osd reporter subtree level``
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:Description: In which level of parent bucket the reporters are counted. The OSDs
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send failure reports to monitor if they find its peer is not responsive.
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And monitor mark the reported OSD out and then down after a grace period.
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:Type: String
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:Default: ``host``
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.. index:: OSD hearbeat
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OSD Settings
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------------
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``osd heartbeat address``
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:Description: An Ceph OSD Daemon's network address for heartbeats.
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:Type: Address
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:Default: The host address.
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``osd heartbeat interval``
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:Description: How often an Ceph OSD Daemon pings its peers (in seconds).
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:Type: 32-bit Integer
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:Default: ``6``
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``osd heartbeat grace``
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:Description: The elapsed time when a Ceph OSD Daemon hasn't shown a heartbeat
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that the Ceph Storage Cluster considers it ``down``.
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This setting has to be set in both the [mon] and [osd] or [global]
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section so that it is read by both the MON and OSD daemons.
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:Type: 32-bit Integer
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:Default: ``20``
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``osd mon heartbeat interval``
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:Description: How often the Ceph OSD Daemon pings a Ceph Monitor if it has no
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Ceph OSD Daemon peers.
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:Type: 32-bit Integer
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:Default: ``30``
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``osd mon report interval max``
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:Description: The maximum time in seconds that a Ceph OSD Daemon can wait before
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it must report to a Ceph Monitor.
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:Type: 32-bit Integer
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:Default: ``120``
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``osd mon report interval min``
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:Description: The minimum number of seconds a Ceph OSD Daemon may wait
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from startup or another reportable event before reporting
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to a Ceph Monitor.
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:Type: 32-bit Integer
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:Default: ``5``
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:Valid Range: Should be less than ``osd mon report interval max``
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``osd mon ack timeout``
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:Description: The number of seconds to wait for a Ceph Monitor to acknowledge a
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request for statistics.
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:Type: 32-bit Integer
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:Default: ``30``
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