Oracle Just Published a Document ID 1558550.1 that talks about an issues that i've had an SR out for 6 months now.
Due to a Linux iostat bug BUG: 1672511 (unpublished) - oda - disk device sdau1 & sdau2 are 100% busy due to avgqu-sz value
This forces host level monitoring to report Critical Disk Busy alerts . This Bug will be fixed in an upcoming release of the the Oracle Database Appliance Software.
This workaround is to disable Disk Activity Busy alert in EM12c. After the issue is resolved the user now has the responsibility to remember to reenable this alert.
The alert in the document makes me laugh though
Once you apply the iostat fix through an upcoming ODA release, make
sure that you re-enable this metric by adding the Warning and Critical
threshold values and applying the changes.