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NetApp Stage KB

Slow CIFS performance due to network congestion

Last Updated:


Applies to

  • ONTAP 9
  • CIFS / SMB


  • Microsoft Excel macro involving files on a CIFS share is slow
  • Less than expected throughput
  • Only one client affected
  • No other applications are affected
  • No error counters increased on related ports and ifgroups in ifstat -a
  • Symptom does not change when vScan and fpolicy are disabled
  • Packet trace indicates:
    • SMB2 latency is increased unidirectionally from ONTAP to client
    • Out of order packets and (fast) retransmissions
    • Congestion control

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