ok, Itamar,  thanks.

now I can understand how the things work.

but I have a question based on the fact that  I have ovirt-engine on version 3.4  and DC and Cluster both are configured on version 3.3 :

- This means that I have "available" features on version 3.4 , but these features just will work when I update DC and Cluster to version 3.4   ?   (this is what I understand, following  Dafna Ron response)

so, to really obtain the benefits of the new version (3.4)  I need to run the commands (yum update ovirt-engine-setup, engine-setup) and also increase the version of compatibility within the datacenter, cluster and host to the version 3.4


- and what I have if only update ovirt-engine  to version 3.4 and not update dc, cluster neither hosts.
I realized changes on ovirt web admin interface,  improvements on icons and maybe new fields.



On Fri, Apr 11, 2014 at 9:56 AM, Itamar Heim <iheim@redhat.com> wrote:
On 04/10/2014 10:50 PM, Tamer Lima wrote:
Hi,


yesterday my ovirt was 3.3
my datacenter and cluster (compatibility version) was aligned with ovirt
3.3


today my ovirt is now 3.4.
and my datacenter and cluster (compatibility version) remains 3.3  (with
the option enabled to change for 3.4)

browsing the ovirt admin page I see 2 occurrences of ovirt version:
datacenter tab  = 3.3
cluster tab  =3.3



I would like to understand what means all these versions, the same
version for a lot of important things, and how my ovirt works/behaves
using different versions.

all my doubts together :
What means datacenter in version 3.3(or lower version) when ovirt is 3.4  ?
what means cluster in version 3.3 when ovirt is 3.4?
what means change the "compatibility version" for datacenter?
what means change the "compatibility version" for cluster?

Gianluca replied with links for specific features.
I'll reply on the general concept:
- a host can be upgraded to a specific 3.x version. it can be in any
  3.y cluster which is <= 3.x
  once the host is upgraded, 3.x host-level features can be used
- a cluster can be upgraded to 3.x once all active hosts in it are at
  least with 3.x.
  once the cluster is upgraded, 3.x cluster-level features can be used
- a data cetner can be upgaeded to 3.x once all clusters in it are at
  least with 3.x
  once the DC is upgraded, 3.x DC-level features can be used

i don't think we have it clearly documented per feture if it is host level, cluster level or DC level. when in doubt, ask...