Chapter 6. Compatibility Level Versions

Each hosts connected to Red Hat Enterprise Virtualization Manager has a version of VDSM installed. A current version of the Manager controls hosts with current or older versions of VDSM.

Virtual machines are migrated from host to host within a cluster. This means the Manager excludes certain features from a current version of VDSM until all hosts within a cluster have the same VDSM version, or more recent, installed.

This concept is represented in the API as a compatibility level for each host, corresponding to the version of VDSM installed. A version element containing major and minor attributes describes a compatibility level.

Once all hosts within a cluster have been upgraded to a certain level, that level's version will appear under a supported_versions element. This indicates the cluster's version is now updatable to that level. Once all clusters within a data center are updated to a given level, the data center is updatable to that level.

Example 6.1. Upgrading compatibility levels from Red Hat Enterprise Virtualization Manager 2.2 to 3.0

The API reports the following compatibility levels for Red Hat Enterprise Virtualization Manager 2.2 instance:

<host ...>
    ...
    <version major="2" minor="2"/>
    ...
</host>

<cluster ...>
    ...
    <version major="2" minor="2"/>
    <supported_versions/>
    ...
</cluster>

<data_center ...>
    ...
    <version major="2" minor="2"/>
    <supported_versions/>
    ...
</data_center>

All hosts within a cluster are updated to VDSM 3.0 and the API reports:

<host ...>
    ...
    <version major="3" minor="0"/>
    ...
</host>

<cluster ...>
    ...
    <version major="2" minor="2"/>
    <supported_versions>
        <version major="3" minor="0"/>
    </supported_versions>
    ...
</cluster>

<data_center ...>
    ...
    <version major="2" minor="2"/>
    <supported_versions/>
    ...
</data_center>

The cluster is now updatable to 3.0 and the API reports:

<cluster ...>
    ...
    <version major="3" minor="0"/>
    <supported_versions/>
    ...
</cluster>

<data_center ...>
    ...
    <version major="2" minor="2"/>
    <supported_versions>
        <version major="3" minor="0"/>
    </supported_versions>
    ...
</data_center>

The API user updates the data center to 3.0. Once upgraded, the API exposes features available in Red Hat Enterprise Virtualization 3.0