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Does the FPolicy Send Buffer need increased due to EAGAIN in ONTAP 9.8 or higher?

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Applies to

  • ONTAP 9.8 or newer
  • FPolicy

Answer

No, in most cases

Additional Information

  • ONTAP 9.7 and older had a rewind on EAGAIN at a fixed 2 seconds
    • The 2 second window created a loop:
      • FPolicy server would have slowness send buffer would fill
      • I/O stayed in queue for 2 seconds each rewind and may take seconds or tens of seconds to process
      • The queue would never clear because of each 2 second rewind, even if the FPolicy server had a temporary performance problem
      • The only way this would stop is if I/O dropped to near zero periods or manual intervention to disable FPolicy
  • ONTAP 9.8's much smaller EAGAIN rewind window allows the queue to clear when the FPolicy server starts responding
  • The following conditions need to be met to consider increasing send buffer size:
    • Latency must be seen on volumes
    • The FPolicy vendor has seen performance is fine
    • The network between ONTAP and the FPolicy server is clean and responsive as determined in a packet trace
    • NetApp Support may recommend to increase outside of the above conditions in specific cases
    • If none of above are true, please follow the guidance in High sustained latency after ONTAP upgrade to 9.8 and above due to FPolicy EAGAIN
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