Chapter 2. Technical Notes

The ovirt-engine service is now used to control the Red Hat Enterprise Virtualization Manager. The jbossas service still exists but IS no longer used to control the Manager. Starting the jbossas service launches a standalone instance of JBoss Enterprise Application Platform 6 and will not start Red Hat Enterprise Virtualization Manager. The jbossas service must not be started on a machine hosting the Manager.

The Manager is now able to automatically detect time drift on virtualization hosts. To use this functionality, set these configuration values using the rhevm-config command:

* EnableHostTimeDrift - Enables time drift detection, the default value is false.
* HostTimeDriftInSec - Sets the maximum time drift allowable, in seconds, before an alert is raised. The default value is 300.

Each time the Manager checks the state of the host it compares the system time of the two systems, expressed in GMT. If EnableHostTimeDrift is true and the manager detects that the times returned differ by more than HostTimeDriftInSec then an alert is written to the log file. 

A "VDS_TIME_DRIFT_ALERT" event is also raised, which can be tracked using the event notification daemon.

Hosts must be moved to maintenance mode before changing their Storage Pool Manager (SPM) priority to '-1' using the REST API, otherwise the change will not take effect. An SPM priority of '-1' indicates the host must never be considered for the SPM role.

When making configuration changes using the rhevm-config tool it is necessary to restart the ovirt-engine service before they will take effect. Additionally changes to values that are cached on the client side require a restart of the client browser to clear cached values before they will take effect.

In environments that contain virtual machine pools it is recommended that you do not assign user roles other than VM_CREATOR, TEMPLATE_CREATOR, and DISK_CREATOR at the system, data center, or cluster level.