vmkwarning: cpu29:66613)WARNING: ScsiDeviceIO: 1188: Device naa.xxx performance has deteriorated. I/O latency increased from average value of 951 microseconds to 20503 microseconds

[bardeg]

I see this in the logs, can someone explain to me how often and how ESXi calculate the latency?

What is average, average of what? How often ESXi is checking the latency?

[msripada]

May be this KB VMware Knowledge Base  can help you a bit better.

Thanks,

MS