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What are the CIFS values to mitigate client malfunction?

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Category:
ontap-9
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nas
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Applies to

  • ONTAP 9
  • CIFS

Answer

The purpose of limits is the lower the chance of a client overwhelming a node in the cluster.

Examples:

EMS message EMS reference Knowledge Base article

Nblade.cifsMaxSessPerUsrConn

 nblade.cifsmaxsessperusrconn events (netapp.com) CIFS shares access may fail and EMS displays error "cifsMaxSessPerUsrConn"
Nblade.cifsSameTreePerSess nblade.cifssametreepersess events (netapp.com)  
Nblade.cifsMaxOpenSameFile nblade.cifsmaxopensamefile events (netapp.com) Error: Nblade.cifsMaxOpenSameFile when CIFS Clients attempt to access files in ONTAP
Nblade.cifsMaxWatchesPerTree  nblade.cifsmaxwatchespertree events (netapp.com)  

Note: Every cluster is different and may require different maximums due to physical constraints. Testing is required.

Additional Information

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  • The default values for these fields were increased in ONTAP 9.3.
  • ONTAP systems upgraded to ONTAP 9.3+ may retain their original default values, though these values can still be modified as necessary
  • Increasing a value is unlikely to cause any issue and should be considered when undesirable behaviour occurs as per above references
  • This may be expected behaviour for services establishing a CIFS session on behalf of multiple users:

Examples:

  • Xen server,
  • IIS server or other web servers

Note: If not expected, client-side investigation with OS/Application vendor needs to be performed

  • Recommendations should come from the Client OS/Application Vendor.
  • Client OS/Application vendor provides no guidance on these values:
    • If there is an expectation that the default value will be exceeded in a natural manner, but there is uncertainty about how the natural behavior will go, then testing higher values will be necessary.
    • There is no perfect method of determining a perfect number to set the value to.
  • One method of testing might be doubling the value, if the error returns, double again, etc.
  • Another method is more slowly increasing the value until the error goes away. (assuming behavior of the OS/application vendor is expected)
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