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  1. Core Server
  2. SERVER-19816

Oplog replication throughput is bounded by network latency

    • Type: Icon: Bug Bug
    • Resolution: Done
    • Priority: Icon: Major - P3 Major - P3
    • None
    • Affects Version/s: 2.6.11, 3.0.5
    • Component/s: Replication
    • Labels:
      None
    • Replication
    • ALL
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      This probably depends on getting exhaust support for both find/getmore commands and makign it available to replication

      Show
      This probably depends on getting exhaust support for both find/getmore commands and makign it available to replication

      Assuming a constant stream of operations totalling 50MB/s data (eg. insertions) to a replica-set, any Secondary that has more than ~40ms network latency (~80ms ping) to its next nearest member will be unable to keep up regardless of the network bandwidth between them.

      If the ping time between any two members of a replica set is known, the upper limit for replication throughput in MB/s between those two members can be calculated with the following equation:

      4 * 1000 / ping_time_in_ms
      

      The limit arises because the tailable cursor retrieves at max 4MB per roundtrip but the request/reply is serial. Thus, the longer a roundtrip (ping) takes, the lower the throughput.

            Assignee:
            backlog-server-repl Backlog - Replication Team
            Reporter:
            andrew.ryder@mongodb.com Andrew Ryder (Inactive)
            Votes:
            3 Vote for this issue
            Watchers:
            24 Start watching this issue

              Created:
              Updated:
              Resolved: