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What do bus overruns mean?

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ontap-9
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nas
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Applies to

ONTAP 9

Answer

  • Bus overruns is a field in ifstat <interface>
  • Bus overruns counts errors of the number of times the adapter's receive FIFO (first-in-first-out) buffer overflowed and a packet was dropped
  • This error occurs when the bus is busy and the adapter cannot transfer data into the host memory
  • Recommendation if bus overruns are seen
    • Monitor for reports of access issues from machines or end users
    • If there are reports of access issues, and packet trace analysis indicates loss on the port as the cause, discuss enabling L2 flow control on filer and switch ports with your networking team
      • Note: Flow control enabled on a filer port does not automatically mean flow control is enabled on the connected switch port
      • TR-4182 and Flow Control Best Practices advises the following
        • Disable flow control on cluster network ports in the Data ONTAP cluster.
        • Flow control on the remaining network ports (the ports that provide data, management, and intercluster connectivity) should be configured to match the settings within the rest of your environment. 
    • Reduce workload in ONTAP

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