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Merge pull request #41335 from noonedeadpunk/doc/stretch_mon

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doc/rados/operations/stretch-mode: Adjust description of mon.e placement

Reviewed-by: Greg Farnum <gfarnum@redhat.com>
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Gregory Farnum 2021-08-23 16:13:54 -07:00 committed by GitHub
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doc/rados/operations/stretch-mode.rst
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@ -94,7 +94,7 @@ named ``site1`` and ``site2``::
} }
Finally, inject the CRUSH map to make the rule available to the cluster:: Finally, inject the CRUSH map to make the rule available to the cluster::
$ crushtool -c crush.map.txt -o crush2.map.bin $ crushtool -c crush.map.txt -o crush2.map.bin
$ ceph osd setcrushmap -i crush2.map.bin $ ceph osd setcrushmap -i crush2.map.bin
@ -104,9 +104,13 @@ the instructions in `Changing Monitor Elections`_.
.. _Changing Monitor elections: ../change-mon-elections .. _Changing Monitor elections: ../change-mon-elections
And lastly, tell the cluster to enter stretch mode. Here, ``mon.e`` is the And lastly, tell the cluster to enter stretch mode. Here, ``mon.e`` is the
tiebreaker and we are splitting across data centers :: tiebreaker and we are splitting across data centers. ``mon.e`` should be also
set a datacenter, that will differ from ``site1`` and ``site2``. For this
purpose you can create another datacenter bucket named ```site3`` in your
CRUSH and place ``mon.e`` there ::
$ ceph mon enable_stretch_mode e stretch_rule data center $ ceph mon set_location e datacenter=site3
$ ceph mon enable_stretch_mode e stretch_rule datacenter
When stretch mode is enabled, the OSDs wlll only take PGs active when When stretch mode is enabled, the OSDs wlll only take PGs active when
they peer across data centers (or whatever other CRUSH bucket type they peer across data centers (or whatever other CRUSH bucket type
@ -132,7 +136,6 @@ restores min_size to its starting value (2) and requires both sites to peer,
and stops requiring the always-alive site when peering (so that you can fail and stops requiring the always-alive site when peering (so that you can fail
over to the other site, if necessary). over to the other site, if necessary).
Stretch Mode Limitations Stretch Mode Limitations
======================== ========================
As implied by the setup, stretch mode only handles 2 sites with OSDs. As implied by the setup, stretch mode only handles 2 sites with OSDs.
@ -172,7 +175,7 @@ when the PGs are healthy. If this doesn't happen, or you want to force the
cross-data-center peering early and are willing to risk data downtime (or have cross-data-center peering early and are willing to risk data downtime (or have
verified separately that all the PGs can peer, even if they aren't fully verified separately that all the PGs can peer, even if they aren't fully
recovered), you can invoke :: recovered), you can invoke ::
$ ceph osd force_healthy_stretch_mode --yes-i-really-mean-it $ ceph osd force_healthy_stretch_mode --yes-i-really-mean-it
This command should not be necessary; it is included to deal with This command should not be necessary; it is included to deal with