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High network latency in an iSCSI SAN environment

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Applies to

  • NetApp FAS/AFF systems
  • iSCSI Protocol

Issue

  • Workloads on hosts accessing LUNs via iSCSI incur significant application and client latency
  • ONTAP has low latency (less than 5 milliseconds) in latency counters
  • Network latency in SAN environment is seen in the Network delay center or Network in Active IQ Unified Manager (AIQUM) but not in Network Processing under the Cluster Components volume view

Example:

qos statistics volume latency show shows high latency in the Network column for three SAN workloads

cluster::> qos statistics volume latency show -node san_node1

Workload        ID    Latency    Network    Cluster       Data       Disk        QoS      NVRAM      Cloud 
----------- ------ ---------- ---------- ---------- ---------- ---------- ---------- ---------- ----------
volume_SAN1  17882     20.51ms    20.51ms      0ms        0ms        0ms        0ms        0ms        0ms  
volume_SAN2   5232     15.00ms    15.00ms      0ms        0ms        0ms        0ms        0ms        0ms  
volume_SAN3  17160     16.00ms    16.00ms      0ms        0ms        0ms        0ms        0ms        0ms

 

 

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