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DOCSP-48515-Source-destination-balancing #678

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DOCSP-48515-Source-destination-balancing #678

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5 changes: 5 additions & 0 deletions source/reference/mongosync/mongosync-behavior.txt
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Expand Up @@ -113,6 +113,11 @@ destination cluster.
Chunk Distribution
''''''''''''''''''

.. important::

Even if ``mongosync`` balances the source cluster, it does not
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I think this language might be a little confusing–mongosync itself doesn't balance the source cluster, it's really that the source cluster was balanced prior to mongosync. This might read better if use the language from the jira ticket like "preserve chunk distribution from the source to the destination", because I think what we're really saying is that even if the source is balanced before mongosync, mongosync doesn't guarantee the destination cluster will be balanced.

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thanks, agree with Nick

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The distinction we want to draw is, even if the source cluster is itself already properly balanced prior to mongosync being called, this pre-existing balance does not help the destination cluster get balanced because mongosync does not preserve the sharding config

necessarily balance the destination cluster.

``mongosync`` does not preserve chunk distribution from the source to
the destination, even with multiple ``mongosync`` instances. It is not
possible to reproduce a particular pre-split of chunks from a source
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