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 NVRAMUser-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 NVRAMUser-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.
Check the following 2 KB articles which give indepth knowledge on Network Configuration and Lun latency.