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"<storage_device> performance has deteriorated" message in ESXi (2007236)

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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


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


High device latency

If the device latency is too high for a consistent period of time, check the storage performance by verifying the logs on the storage array for any indication of a failure. If failures are logged on the storage array side, take corrective actions. Contact your storage vendor for information regarding checking logs on the array.

Also, check if these messages are generated when there were any scheduled tasks, such as backups or replications, as these can also cause intermittent performance hits.

Overload conditions on the device

If the message is generated because of an overload condition, attempt to reduce the load on the affected storage device.
LUN replication tool is running

 If running a LUN replication tool, pause the task from the storage end and attempt a storage vMotion to a different datastore. This should help improve the I/O operations.

See Also

For translated versions of this article, see: 


storage performance deteriorated, i/o latency, storage latency on RDM disk, device performance has deteriorated, storage latency esxi

Update History

12/13/2012 - Added LUN replication tool note 03/12/2013 - Added ESXi 5.1.x

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