Opening files in ONTAP CIFS shares takes longer when Qtree oplock is disabled

Applies to

ONTAP 9

Issue

• Opening files in specific CIFS shares are slow on Microsoft Windows clients for any file type (PDF, Microsoft Office files, etc.)
• Slowness when opening affected files may be exhibited via VPN and not via direct connection
• Opening specific files (xlsb, pptx, xlsx, docx) is significantly slower than others (txt, xls, pdf,..)
• Newly created SVMs sharing volumes via CIFS are not affected
• ​​​The issue is not spread across the volume rather it is particular share/qtree level issue only.
• No abnormal volume or protocol latency 
  • Follow below steps prior looking into qtree level options

1. Run qos command to verify the volume latency is optimal and compare with historical data e.g. in OCUM
   
   Example:
    
   qos statistics volume latency show -volume Volumename -vserver VStest
    
   Workload            ID    Latency    Network    Cluster       Data       Disk        QoS      NVRAM
--------------- ------ ---------- ---------- ---------- ---------- ---------- ---------- ----------
-total-              -   541.00us   125.00us    42.00us    84.00us   273.00us        0ms    17.00us
Volumename..      ####   182.00us    61.00us        0ms    78.00us    43.00us        0ms        0ms
-total-              -   744.00us   430.00us    69.00us    79.00us   153.00us        0ms    13.00us
Volumename..      ####   180.00us    63.00us        0ms    77.00us    40.00us        0ms        0ms
-total-              -   260.00us    62.00us    54.00us    85.00us    44.00us        0ms    15.00us
Volumename..      ####   192.00us    61.00us        0ms    84.00us    47.00us        0ms        0ms
-total-              -   506.00us    77.00us    48.00us   211.00us   170.00us        0ms        0ms
Volumename..      ####   365.00us    61.00us        0ms   218.00us    86.00us        0ms        0ms
2. Check CIFS SVM level stats (this may be verified for SMBb2 object as well):

statistics show-periodic -object cifs -instance VStest -node NodeA -counter cifs_ops|cifs_read_ops|cifs_write_op

• Confirm from above command if there is any delay at the storage level. 
• If not, verify the Qtree level options because the issue only appears on specific shares