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Latency from CPU_protocol for extremely bursty SAN workloads

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ontap-9
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perf
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Applies to

ONTAP 9

Issue

  • High latency observed for extremely bursty SAN workloads. Breakdown of the latency shows high latency on Network & Protocol processing, this could be observed in various ways:
    • Perfstat: Delay from CPU_protocol
    • PerfArchive: Delay from Network
    • Other performance monitoring tools like NetApp Harvest/Grafana will have similar latency breakdowns. 
    • Command Line: qos statistics workload latency show or qos statistics volume latency show has the latency from Network

Example:

Latency from CPU_protocol for extremely bursty SAN workloads

  • The high latency from CPU_protocol/Network is observed when there is no CPU contention in SAN processing CPU Domains, such as SSAN_Ex. 

Example: sysstat -M 1(Diag Mode)

Latency from CPU_protocol for extremely bursty SAN workloads

Note: If there is an overall CPU contention, then the delay from CPU_protocol/Network is expected, the discussion here wouldn't apply. 

  • The following KB would help detect if there exists an extremely bursty workload

How to identify transient workload bursts using "sysstat" command

 

 

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