How ONTAP implements SMB crediting
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
- As documented in this Microsoft Docs page, Performance tuning for SMB file servers, Windows now defaults to 512 credits.
- 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
- 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.
- 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.
- What value should be chosen?
For assistance with disabling SMB crediting, contact NetApp Technical Support and reference this article.