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  1. Core Server
  2. SERVER-14003

2.6 mongos does not support overlapped writes at w:0

    • Type: Icon: New Feature New Feature
    • Resolution: Won't Fix
    • Priority: Icon: Critical - P2 Critical - P2
    • None
    • Affects Version/s: 2.6.1
    • Component/s: Sharding
    • None
    • Sharding

      Shows up as a performance degradation for applications that use w:0 and getLastError in a sharded environment when going from 2.4 to 2.6:

      To reproduce: create a collection, mongodump, mongorestore via mongos to single-shard cluster (single mongod, single config server). Doesn't seem to matter if collection is sharded or not.

      Here are some numbers for one data set:

      2.4.10, standalone                      26s
      2.6.1, standalone                       26s
      2.4.10, 1x shard, 1x mongos, sharded    58s
      2.6.1, 1x shard, 1x mongos, sharded    352s
      

      Another data set, showing that sharded or unsharded shows same degradation:

      2.4.10, standalone                       5s
      2.6.1, standalone                        5s
      2.4.10, 1x shard, 1x mongos, unsharded   5s
      2.6.1, 1x shard, 1x mongos, unsharded   45s
      2.4.10, 1x shard, 1x mongos, sharded     8s
      2.6.1, 1x shard, 1x mongos, sharded     52s
      

            Assignee:
            backlog-server-sharding [DO NOT USE] Backlog - Sharding Team
            Reporter:
            bruce.lucas@mongodb.com Bruce Lucas (Inactive)
            Votes:
            4 Vote for this issue
            Watchers:
            25 Start watching this issue

              Created:
              Updated:
              Resolved: