[ovirt-users] VM paused rather than migrate to another hosts

[Terry hey]

Dear Milan,

Thank you for your explanation.
Very clear!

Regards,
Terry

2018-03-02 0:03 GMT+08:00 Milan Zamazal <mzamazal at redhat.com>:

> Terry hey <recreationh at gmail.com> writes:
>
> > Dear Milan,
> > Today, i just found that oVirt 4.2 support iLO5 and power management was
> > set on all hosts (hypervisor).
> > I found that if i choose VM lease and shutdown iSCSI network, the VM was
> > shutdown.
> > Then the VM will migrate to another host if the iSCSI network was
> resumed.
>
> If the VM had been shut down then it was probably restarted on rather
> than migrated to another host.
>
> > If i just choose enable HA on VM setting, the VM was successfully migrate
> > to another hosts.
>
> There can be a special situation if the storage storing VM leases is
> unavailable.
>
> oVirt tries to do what it can in case of storage problems, but it all
> depends on the overall state of the storage – for how long it remains
> unavailable, if it is available at least on some hosts, and which parts
> of the storage are available; there are more possible scenarios here.
> Indeed, it's a good idea to experiment with failures and learn what
> happens before real problems come!
>
> > But i want to ask another question, what if the management network is
> down?
> > What VM and hosts behavior would you expect?
>
> The primary problem is that oVirt Engine can't communicate with the
> hosts in such a case.  Unless there is another problem (especially
> assuming storage is still reachable from the hosts) the hosts and VMs
> will keep running, but the hosts will be displayed as unreachable and
> VMs as unknown in Engine.  And you won't be able to manage your VMs from
> Engine of course.  Once the management network is back, things should
> return to normal state sooner or later.
>
> Regards,
> Milan
>
> > Regards
> > Terry Hung
> >
> > 2018-02-28 22:29 GMT+08:00 Milan Zamazal <mzamazal at redhat.com>:
> >
> >> Terry hey <recreationh at gmail.com> writes:
> >>
> >> > I am testing iSCSI bonding failover test on oVirt, but i observed
> that VM
> >> > were paused and did not migrate to another host. Please see the
> details
> >> as
> >> > follows.
> >> >
> >> > I have two hypervisors. Since they are running iLO 5 and oVirt 4.2
> cannot
> >> > support iLO 5, thus i cannot setup power management.
> >> >
> >> > For the cluster setting, I set "Migrate Virtual Machines" under the
> >> > Migration Policy.
> >> >
> >> > For each hypervisor, I bonded two iSCSI interface as bond 1.
> >> >
> >> > I created one Virtual machine and enable high availability on it.
> >> > Also, I created one Virtual machine and did not enable high
> availability
> >> on
> >> > it.
> >> >
> >> > When i shutdown one of the iSCSI interface, nothing happened.
> >> > But when i shutdown both iSCSI interface, VM in that hosts were paused
> >> and
> >> > did not migrate to another hosts. Is this behavior normal or i miss
> >> > something?
> >>
> >> A paused VM can't be migrated, since there are no guarantees about the
> >> storage state.  As the VMs were paused under erroneous (rather than
> >> controlled such as putting the host into maintenance) situation,
> >> migration policy can't help here.
> >>
> >> But highly available VMs can be restarted on another host automatically.
> >> Do you have VM lease enabled for the highly available VM in High
> >> Availability settings?  With a lease, Engine should be able to restart
> >> the VM elsewhere after a while, without it Engine can't do that since
> >> there is danger of resuming the VM on the original host, resulting in
> >> multiple instances of the same VM running at the same time.
> >>
> >> VMs without high availability must be restarted manually (unless storage
> >> domain becomes available again).
> >>
> >> HTH,
> >> Milan
> >>
>
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