Chapter 4. Overrides
By default, Ceph will reflect the current status of OSDs and perform normal operations such as rebalancing, recovering, and scrubbing. From time to time, it may be advantageous to override Ceph’s default behavior.
4.1. Setting and Unsetting Overrides
To override Ceph’s default behavior, use the ceph osd set command and the behavior you wish to override. For example:
# ceph osd set <flag>
Once you set the behavior, ceph health will reflect the override(s) that you have set for the cluster.
To cease overriding Ceph’s default behavior, use the ceph osd unset command and the override you wish to cease. For example:
# ceph osd unset <flag>
| Flag | Description |
|---|---|
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Prevents OSDs from being treated as |
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Prevents OSDs from being treated as |
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Prevents OSDs from being treated as |
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Prevents OSDs from being treated as |
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Makes a cluster appear to have reached its |
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Ceph will stop processing read and write operations, but will not affect OSD |
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| Ceph will prevent new backfill operations. |
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| Ceph will prevent new rebalancing operations. |
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| Ceph will prevent new recovery operations. |
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| Ceph will prevent new scrubbing operations. |
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| Ceph will prevent new deep scrubbing operations. |
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| Ceph will disable the process that is looking for cold/dirty objects to flush and evict. |
4.2. Use Cases
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noin: Commonly used withnooutto address flapping OSDs. -
noout: If themon osd report timeoutis exceeded and an OSD has not reported to the monitor, the OSD will get markedout. If this happens erroneously, you can setnooutto prevent the OSD(s) from getting markedoutwhile you troubleshoot the issue. -
noup: Commonly used withnodownto address flapping OSDs. -
nodown: Networking issues may interrupt Ceph 'heartbeat' processes, and an OSD may beupbut still get marked down. You can setnodownto prevent OSDs from getting marked down while troubleshooting the issue. -
full: If a cluster is reaching itsfull_ratio, you can pre-emptively set the cluster tofulland expand capacity. NOTE: Setting the cluster tofullwill prevent write operations. -
pause: If you need to troubleshoot a running Ceph cluster without clients reading and writing data, you can set the cluster topauseto prevent client operations. -
nobackfill: If you need to take an OSD or nodedowntemporarily, (e.g., upgrading daemons), you can setnobackfillso that Ceph will not backfill while the OSD(s) isdown. -
norecover: If you need to replace an OSD disk and don’t want the PGs to recover to another OSD while you are hotswapping disks, you can setnorecoverto prevent the other OSDs from copying a new set of PGs to other OSDs. -
noscrubandnodeep-scrubb: If you want to prevent scrubbing (e.g., to reduce overhead during high loads, recovery, backfilling, rebalancing, etc.), you can setnoscruband/ornodeep-scrubto prevent the cluster from scrubbing OSDs. -
notieragent: If you want to stop the tier agent process from finding cold objects to flush to the backing storage tier, you may setnotieragent.
