AVGQU-SZ or disk utilization very high in iostat or EM Disk Device Busy metric, without corresponding disk activity (Doc ID 1583552.1)

Last updated on MARCH 06, 2016

Applies to:

Linux OS - Version 2.6.18 to Oracle Linux 5.9 with Unbreakable Enterprise Kernel [2.6.32]
Linux OS - Version Oracle Linux 5.5 to Oracle Linux 5.9 [Release OL5U5 to OL5U9]
Linux x86-64

Symptoms

This is generally seen when monitoring disk activity with iostat, or when an EM alert is received for Disk Device Busy (%) .   For example, sample iostat output would look like:


As can be seen, there are no reads or writes taking place (r/s or w/s) for the device, yet the avgqu-sz is very large with a corresponding 100% utilization.

For an example of the EM alert please see Doc ID 1558550.1 .

Cause

Sign In with your My Oracle Support account

Don't have a My Oracle Support account? Click to get started

My Oracle Support provides customers with access to over a
Million Knowledge Articles and hundreds of Community platforms