ESXi host reports this message when the latency on the device is higher than the average latency:
Device naa.5000c5000b36354b performance has deteriorated. I/O latency increased from average value of 1832 microseconds to 19403 microsecond
Cause
This occurs when either the latency ratio to the last time the log was updated is 30 or if the ratio doubled since the last log. The device latency may increase due to one of these reasons:
- Changes made on the target
- Disk or media failures
- Overload conditions on the device
- Failover