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DOCS-1775: Add some caution notes regarding creating a new hashed collec... #1212

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29 changes: 19 additions & 10 deletions source/tutorial/shard-collection-with-a-hashed-shard-key.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,10 @@ Shard a Collection Using a Hashed Shard Key

.. default-domain:: mongodb

.. contents::
:backlinks: none
:local:

.. versionadded:: 2.4

:ref:`Hashed shard keys <sharding-hashed-sharding>` use a :ref:`hashed
Expand All @@ -14,11 +18,15 @@ For tips on choosing the right field as your hashed shard key, see
:ref:`sharding-hashed-sharding`. For limitations on hashed indexes, see
:ref:`index-hashed-index`.

Basic Procedure
---------------
.. note:: If chunk migrations are in progress while creating a hashed shard key
collection, the initial chunk distribution may be unbalanced until the
balancer automatically balances the collection.

Shard the Collection
--------------------

To shard a collection using a hashed shard key, issue an operation in
the :program:`mongo` shell that resembles the following:
Do an operation in the :program:`mongo` shell that resembles the
following:

.. code-block:: javascript

Expand All @@ -31,14 +39,15 @@ Specify the Initial Number of Chunks
------------------------------------

If you shard an empty collection using a hashed shard key, MongoDB
automatically creates and migrate chunks so that each shard has two
chunks. You can control how many chunks MongoDB creates sharding the
collection using :dbcommand:`shardCollection` with the
automatically creates and migrates empty chunks so that each shard
has two chunks. To control how many chunks MongoDB creates when
sharding the collection, use :dbcommand:`shardCollection` with the
``numInitialChunks`` parameter.

.. include:: /includes/warning-hashed-index-floating-point.rst

.. important:: MongoDB 2.4 add support for hashed shard keys. After
.. important:: MongoDB 2.4 adds support for hashed shard keys. After
sharding a collection with a hashed shard key, you must use the
MongoDB 2.4 or higher :program:`mongos` and :program:`mongod`
instances in your sharded cluster.

.. include:: /includes/warning-hashed-index-floating-point.rst