[ovirt-users] VDSM multipath.conf - prevent automatic management of local devices

[Nir Soffer]

On Tue, Nov 28, 2017 at 12:25 AM Ben Bradley <listsbb at virtx.net> wrote:

> On 23/11/17 06:46, Maton, Brett wrote:
> > Might not be quite what you're after but adding
> >
> > # RHEV PRIVATE
> >
> > To /etc/multipath.conf will stop vdsm from changing the file.
> > |||
>
> Hi there. Thanks for the reply.
> Yes I am aware of that and it seems that's what I will have to do.
> I have no problem with VDSM managing the file, I just wish it didn't
> automatically load local storage devices into multipathd.
>

We don't load anything, this is multipathd default behavior.

We cannot blacklist local devices since we don't know which devices
are local, this is something the administrator of the machine should handle.

In RHEL/CentOS 7.5 we will have a good way to blacklist most local devices,
see https://bugzilla.redhat.com/show_bug.cgi?id=1456955#c0

Once this is available, your multipath.conf will be upgrade to use the
new feature when you upgrade vdsm.


>
> I'm still not clear on the purpose of this automatic management though.
>  From what I can tell there is no difference to hosts/clusters made
> through this automatic management - i.e. you still have to add storage
> domains manually in oVirt.
>

The purpose of this configuration is to allow Vdsm to manage shared
storage - we require certain configuration.

In 4.2 we documented every setting in multipath.conf, please see
https://github.com/oVirt/vdsm/blob/913c2e202de718ec828b240642e37e059a86dac9/lib/vdsm/tool/configurators/multipath.py#L66
to understand why we require each value.

If the default multiapth.conf does not work for you, you can make the file
private, and then you are responsible for using new features provided
by multipath, we will never touch the file.

You can also file a bug if you think the default configuration can be
improved to support some use case.

Nir


>
> Could anyone give any info on the purpose of this auto-management of
> local storage devices into multipathd in VDSM?
> Then I will be able to make an informed decision as to the benefit of
> letting it continue.
>
> Thanks, Ben
>
> >
> > On 22 November 2017 at 22:42, Ben Bradley <listsbb at virtx.net
> > <mailto:listsbb at virtx.net>> wrote:
> >
> >     Hi All
> >
> >     I have been running ovirt in a lab environment on CentOS 7 for
> >     several months but have only just got around to really testing
> things.
> >     I understand that VDSM manages multipath.conf and I understand that
> >     I can make changes to that file and set it to private to prevent
> >     VDSM making further changes.
> >
> >     I don't mind VDSM managing the file but is it possible to set to
> >     prevent local devices being automatically added to multipathd?
> >
> >     Many times I have had to flush local devices from multipath when
> >     they are added/removed or re-partitioned or the system is rebooted.
> >     It doesn't even look like oVirt does anything with these devices
> >     once they are setup in multipathd.
> >
> >     I'm assuming it's the VDSM additions to multipath that are causing
> >     this. Can anyone else confirm this?
> >
> >     Is there a way to prevent new or local devices being added
> >     automatically?
> >
> >     Regards
> >     Ben
> >     _______________________________________________
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> >     Users at ovirt.org <mailto:Users at ovirt.org>
> >     http://lists.ovirt.org/mailman/listinfo/users
> >     <http://lists.ovirt.org/mailman/listinfo/users>
> >
> >
>
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