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Clarify when config servers are read-only during csrs upgrade #2563

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Clarify when config servers are read-only during csrs upgrade #2563

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aaa3c13
Clarify when config servers are read-only during csrs upgrade
stbrody Mar 8, 2016
78ed9f2
Update upgrade-config-servers-to-replica-set.txt
stbrody Mar 8, 2016
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15 changes: 15 additions & 0 deletions source/tutorial/upgrade-config-servers-to-replica-set.txt
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Expand Up @@ -25,6 +25,14 @@ The following procedure upgrades three mirrored config servers to a
procedure, all the sharded cluter binaries must be at least version
3.2.4.

During this procedure there will be a period of time where
the config servers will be read-only. During this period, certain catalog
operations will fail if attempted. Operations that will
not be available include adding and dropping shards, creating and dropping
databases, creating and dropping sharded collections, and migrating chunks
(both manually and via the balancer process). Normal read and write
operations to existing collections will not be affected.

.. seealso:: :doc:`/tutorial/upgrade-config-servers-to-replica-set-downtime`

Prerequisites
Expand Down Expand Up @@ -210,6 +218,9 @@ Procedure
#. Shut down one of the other non-replica set config servers; i.e.
either the second and third config server listed in the
:setting:`~sharding.configDB` setting of the :program:`mongos`.
At this point the config servers will go read-only, meaning certain
operations - such as creating and dropping databases and sharded
collections - will not be available.

#. Reconfigure the replica set to allow all members to vote and have
default priority of ``1``.
Expand Down Expand Up @@ -264,6 +275,10 @@ Procedure

If the first config server uses the MMAPv1 storage engine, the
member will transition to ``"REMOVED"`` state.

At this point the config server data will return to being writeable and all
catalog operations - including creating and dropping databases and
sharded collections - will once again be possible.

#. Restart :program:`mongos` instances with updated :option:`--configdb` or
:setting:`sharding.configDB` setting.
Expand Down