Elevated CPU or high cluster latency when using indirect traffic using CIFS or NFS

Applies to

• ONTAP 9
• CIFS
• NFS

Issue

• Slowness may be seen for users.
• Elevated CPU observed when using indirect traffic, specifically the max of Network Exempt.
  • Example:
    • Running the sysstat -M command shows high CPU in Nwk_Exmpt or Network Exempt CPU domain.
    • The sysstat -x 1 output shows 99% CPU, meaning the system is maxed out on CPU or the Network Exempt domain is maxed out.
  • Note: output is missing columns for readability in this article

Cluster::> set advanced

Warning: These advanced commands are potentially dangerous; use them only when directed to do so by NetApp personnel.
Do you want to continue? {y|n}: y

Cluster::*> node run -node <node> sysstat -M 1
AVG Nwk_Exmpt
61% 994%
60% 988%
60% 974%
61% 971%

Cluster::*> node run -node <node> sysstat -x 1
 CPU
     
 99%
 99%
 99%

• An alert may be seen from Active IQ Unified Manager of higher latency being breached
  • Example: Latency value of 12.2 ms/op on Cluster1_N6 has triggered a WARNING event based on threshold setting of 10.0 ms/op.
• Unable to perform upgrade due to high CPU utilization coming from nwk_exempt.
• High latency may also be seen in the cluster network

cluster1::> qos statistics volume latency show -iterations 100
Workload        ID      Latency  Network  Cluster   Data     Disk     QoS       NVRAM      Cloud
--------------- ------ -------- -------- -------- -------- -------- -------- ---------- ----------
-total-                110.35ms    0ms   110.02ms 327.00us      0ms      0ms        0ms        0ms
vs1vol0         111    167.82ms    0ms   167.22ms 603.00us      0ms      0ms        0ms        0ms
vol1            1234   117.76ms    0ms   117.56ms 191.00us      0ms      0ms        0ms        0ms