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The MDS Autoscaler provides automation to maintain a required count of MDSs in the system. The MDS count in the system can be afected by: * max_mds config option * standby_count_wanted config option * death of an active MDS Rank Fixes: https://tracker.ceph.com/issues/46884 Signed-off-by: Milind Changire <mchangir@redhat.com>
32 lines
1.4 KiB
ReStructuredText
32 lines
1.4 KiB
ReStructuredText
MDS Autoscaler Module
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=====================
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The MDS Autoscaler Module monitors ``fsmap`` update notifications from the mgr
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daemon and takes action to spawn or kill MDS daemons for a file-system as per
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changes to the:
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- ``max_mds`` config value
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- ``standby_count_wanted`` config value
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- standby promotions to active MDS state in case of active MDS rank death
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Bumping up the ``max_mds`` config option value causes a standby mds to be promoted
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to hold an active rank. This leads to a drop in standby mds count. The MDS
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Autoscaler module detects this deficit and the orchestrator module is notified
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about the required MDS count. The orchestrator back-end then takes necessary
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measures to spawn standby MDSs.
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Dropping the ``max_mds`` config option causes the orchestrator back-end to kill
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standby mds to achieve the new reduced count. Preferably standby mds are chosen
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to be killed when the ``max_mds`` count is dropped.
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An increment and decrement of the ``standby_count_wanted`` config option value
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has a similar effect on the total MDS count. The orchestrator is notified about
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the change and necessary action to spawn or kill standby MDSs is taken.
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A death of an active MDS rank also causes promotion of a standby mds to occupy
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the required active rank. The MDS Autoscaler notices the change in the standby
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mds count and a message is passed to the orchestrator to maintain the necessary
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MDS count.
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NOTE: There is no CLI associated with the MDS Autoscaler Module.
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