[ovirt-devel] el6 future in ovirt-3.6

[Dan Kenigsberg]

On Wed, Mar 18, 2015 at 09:39:45PM +0200, Sahina Bose wrote:
> 
> On 03/17/2015 11:12 PM, Dan Kenigsberg wrote:
> >On Mon, Mar 16, 2015 at 06:02:36PM +0200, Sahina Bose wrote:
> >>On 03/16/2015 03:28 PM, Dan Kenigsberg wrote:
> >>>Current master branch of vdsm (destined for our 3.6 release) uses el7 as
> >>>its main platform. New features are expected to be available only on el7
> >>>(and modern Fedoras) but not on el6.
> >>>
> >>>On el6, vdsm still builds, runs, and exports clusterLevel <= 3.5, with
> >>>no feature loss relative to 3.5. This has been done per gluster request.
> >>>
> >>>However, maintaining this furhter as high costs: we keep testing el6, we
> >>>need to make sure nothing breaks there, and there's a lot of legacy code
> >>>that we could start deleting.
> >>>
> >>>Sahina, would you explain (again... sorry for not recalling the details)
> >>>why ovirt-3.6's vdsm should keep running on el6? I'd like to see if
> >>>there's a nother means to solve the underlying gluster issue.
> >>This was only because downstream gluster + vdsm would continue to be
> >>supported on RHEL 6.
> >Could you provide more details about your needs? Catering for d/s RHS is
> >very important, but since it's expensive to maintain, I'd like to
> >understand more.
> >
> >Please note again that when installed on el6, ovirt-3.6's vdsm would NOT
> >expose clusterLevel=3.6, so theoretically you can keep ovirt-3.5's vdsm.
> >
> >Do you plan an Engine-side hack in order to use new 3.6 gluster functionality
> >despite clusterLevel<=3.5?
> 
> 
> I wasn't aware that ovirt-3.6 would not expose clusterLevel 3.6 when
> installed on el6.
> Downstream RHS will need to be supported on both el6 and el7. And we have
> added some apis to vdsm master that we require for brick management, geo-rep
> management and gluster volume snapshot management.
> We have 2 options
> - fork off vdsm if it needs to move on to el7 support only in master.

We (developers) WANT to shed off el7. But RHS is an important user;
and there are other users that are simply happy to use el6 and don't
want to desert it yet.

We can keep el6 support even on 3.6 (with clusterLevel=3.5).

The only problem (beside maintanence cost) is how gluster can tell these
hosts apart. Can Engine manage a clusterLevel=3.5.5? Vdsm-3.6 can report
it even on el6 hosts.

> - backport to vdsm 3.5 (depending on what we decide on cluster level support
> for downstream)

I find it dangerous to introduce new features to a stable branch. It may
introduce unwarrented instability to non-gluster users.