Large network latency

nicholas4704 — Wed, 04 Jun 2025 22:41:48 GMT

On a FAS2520 iSCSI attached storage (1Gbps active link, 1Gbps passive). 10G Base-T ports used on 1Gbps speed. Switch Cisco SG500. Host is - VMware esx.

I see high latencies. VMware latency are up to 25ms, I think it is because vmware averages that.

qos statistics shows high latency on network layer. Can anybody explain what can cause high network latency?

qos statistics latency show output, latency can be up to 140ms, but is much lower in avg.

Policy Group Latency Network Cluster Data Disk QoS NVRAM
User-Best-Effort 46.53ms 45.11ms 0ms 301.00us 87.00us 0ms 1033.00us

It is not because 1Gbps is full see statistics run from two CLI windows simultaneously:

Latency up to 23ms:

qos statistics latency show

Policy Group Latency Network Cluster Data Disk QoS NVRAM
User-Best-Effort 22.96ms 22.11ms 0ms 210.00us 71.00us 0ms 573.00us

No much output:

qos statistics performance show

Policy Group IOPS Throughput Latency

User-Best-Effort 202 8.77MB/s 23.26ms

I did not find any errors in ifstat -a output. Links run at 1Gbps.

Thank you.

Nick

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Large network latency

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