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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::
$ crushtool -c crush.map.txt -o 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
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
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
over to the other site, if necessary).
Stretch Mode Limitations
========================
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
verified separately that all the PGs can peer, even if they aren't fully
recovered), you can invoke ::
$ ceph osd force_healthy_stretch_mode --yes-i-really-mean-it
This command should not be necessary; it is included to deal with