[ovirt-users] massive simultaneous vms migrations ?

[Yaniv Kaul]

On Tue, Apr 18, 2017 at 7:48 PM, Nelson Lameiras <
nelson.lameiras at lyra-network.com> wrote:

> hello,
>
> When putting a host on "maintenance mode", all vms start migrating to
> other hosts.
>
> We have some hosts that have 60 vms. So this will create a 60 vms
> migrating simultaneously.
> Some vms are under so much heavy loads that migration fails often (our
> guess is that massive simultaneous migrations does not help migration
> convergence) - even with "suspend workload if needed" migraton policy.
>
> - Does oVirt really launches 60 simultaneous migrations or is there a
> queuing system ?
> - If there is a queuing system, is there a way to configure a maximum
> number of simultaneous migrations ?
>
> I did see a "migration bandwidth limit", but this is quite what we are
> looking for.
>

What migration policy are you using?
Are you using a dedicated migration network, or the ovirtmgmt network?


>
> my setup:
> ovirt-engine +hosted engine 4.1.1
> hosts : centos 7.3 fully updated.
>
> for full context to understand this question : 2 times in the past, when
> trying to put a host in maintenance, host stopped responding during massive
> migrations and was fenced by engine. It's still unclear why host stopped
> responding, but we think that migrating 60+ vms simultaneously puts a heavy
> strain on storage ? So we would like to better control migration process in
> order to better understand what's happening. This scenario is "production
> only" since our labs do not contain nearly as much vm with such heavy
> loads. So rather than trying to reproduce, we are trying to avoid ;)
>

If you could open a bug with relevant logs on the host not responding,
that'd be great.
Live migration doesn't touch the storage (disks re not moving anywhere),
but it does stress the network. I doubt it, but perhaps you over-saturate
the ovirtmgmt network.
Y.


>
> cordialement, regards,
>
> <https://www.lyra-network.com/>
> Nelson LAMEIRAS
> Ingénieur Systèmes et Réseaux / Systems and Networks engineer
> Tel: +33 5 32 09 09 70 <+33%205%2032%2009%2009%2070>
> nelson.lameiras at lyra-network.com
> www.lyra-network.com | www.payzen.eu <https://payzen.eu>
> <https://www.youtube.com/channel/UCrVl1CO_Jlu3KbiRH-tQ_vA>
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> <https://twitter.com/LyraNetwork>
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