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How ONTAP implements SMB crediting

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Applies to

  • ONTAP 9.4 and later
  • SMB2 and higher

Answer

  • In ONTAP 9.4, throttling of SMB credits was implemented via a maximum credits configuration
    • Prior to 9.4, SMB clients were granted as many credits as they requested
    • By default, ONTAP 9.4 grants 128 credits per connection
  • How to confirm the current max-credits value:

cluster1::*> set -privilege advanced
cluster1::*> vserver cifs options show -vserver svm1 -fields max-credits

  • How to modify max-credits value

cluster1::*> vserver cifs options modify -vserver svm1 -max-credits 512

Additional Information

  • Modified credit value will only take effect on new cifs sessions
  • The allowed range is between 2 and 8192
    • What value should be chosen?
      • Default value does not need to be changed unless issue is confirmed to be root cause or vendor states X number of credits are needed.
        • Follow client vendor recommendations if it differs from the default
        • Test with client application on a test SVM by slowly increasing the value until the issue is resolved
        • While it is possible to set number of credits to 2, there have been reports that some clients start to misbehave with such a low setting
    • Should I expect any problems when changing the value?
      • No, we don't expect the change to cause any issues
      • To be safe, make the changes on a test SVM with test clients prior to making the change on a production SVM.

For assistance with disabling SMB crediting, contact NetApp Technical Support and reference this article.

 

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