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DOCS-1589: Document the impact of having a hidden node being stopped and... #1236

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DOCS-1589: Document the impact of having a hidden node being stopped and... #1236

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32 changes: 17 additions & 15 deletions source/core/replica-set-hidden-member.txt
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Expand Up @@ -17,23 +17,25 @@ members in the :term:`replica set`. Hidden members are also
display hidden members. Hidden members, however, **do vote** in
:ref:`elections <replica-set-elections>`.

In the following five-member replica set, all four secondary
members have copies of the primary's data set, but one of secondary
members is hidden.
In the following five-member replica set, all four secondary members
have copies of the primary's data set, but one of the secondary members
is hidden.

.. include:: /images/replica-set-hidden-member.rst

Secondary reads do not reach a hidden member, so the member receives
no traffic beyond what replication requires. Use hidden members for
instances that require separation from normal traffic. For example,
you might use hidden members for instances dedicated to reporting or
to backups.

For dedicated backup, ensure that the hidden member has low network
latency to network to the primary or likely primary. Ensure that the
:term:`replication lag` is minimal or non-existent. For more
information about backing up MongoDB databases, see
:doc:`/core/backups`.

To configure a hidden member, see
no traffic beyond what replication requires. It can be useful to keep a hidden
member dedicated to reporting or to do backups.

For dedicated backup, ensure that the hidden member has low
network latency to the primary or likely primary. Ensure that the
:term:`replication lag` is minimal or non-existent.

It is best not to shut down a hidden node. Instead, for filesystem
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avoid using the term "node" to refer to a member of a mongodb deployment (cluster/shard/instance/etc.)

snapshots, it is preferable to use :method:`db.fsyncLock()` to flush all
writes and lock the :program:`mongod` instance for the duration of the
backup.

For more information about backing up MongoDB databases,
see :doc:`/core/backups`. To configure a hidden member, see
:doc:`/tutorial/configure-a-hidden-replica-set-member`.