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  1. Documentation
  2. DOCS-15792

[Server] Migration thresholds are missing from Sharded Cluster Balancer topic

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    • Icon: Task Task
    • Resolution: Fixed
    • Icon: Critical - P2 Critical - P2
    • Server_Docs_20231030
    • 6.0.0
    • Server
    • None

    Description

      Currently balancing threshold are not clarified and the section contains a link to itself:

      https://www.mongodb.com/docs/manual/core/sharding-balancer-administration/#std-label-sharding-migration-thresholds

      Also, the "migration thresholds" link points to the same section - that should be fixed/removed.

      Explanation provided by engineering
      The migration threshold for 6.0 is 3x the configured chunk size for a given collection. So for the default chunk size (for 6.0) of 128MB, two shards must have a data size difference for a given collection of at least 384MB for a migration to occur.

      At steady state it's ok to have shards' data sizes slightly differing. Much better than continuously moving data to reach perfect equality.

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            joseph.dougherty@mongodb.com Joseph Dougherty
            dmitry.ryabtsev@mongodb.com Dmitry Ryabtsev
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            Dates

              Created:
              Updated:
              Resolved:
              43 weeks, 1 day ago