[ovirt-users] Migration Failure Due to network

[Michal Skrivanek]

> On 20 Jul 2016, at 15:22, Alexis HAUSER <alexis.hauser at telecom-bretagne.eu> wrote:
> 
>> Use "Clusters" -> "Logical Networks" -> "Manage Networks" for assigning
>> network for migrations. It's ovirtmgmt by default. Note that migration
>> network has to have IPs on hosts.
> 
> Nice, do you think I should dedicate a link only for migration, for safety ?
> 
> 
>> Hosts have VDSM configuration option - [vars]/migration_max_bandwidth
>> in /etc/vdsm/vdsm.conf. It's 52MB/s by default. So it looks like your
>> network is already highly used.
> 
> It's not highly used, it's yet on a 10/100 Mb switch...But it's just temporary. Anyway it's interesting because it simulates a highly use network, which can happen.
> 
> 
>> Your VM migration fails because migration is so slow so it just can't
>> migrate without downtime. You can adjust "Use custom migration
>> downtime" VM option to make any VM migrated over any network. Please
>> note it's a maximal value. Actually it starts with a value 10 times
>> lower and increases it automatically. 5000 is good value to start in
>> your case.
> 
> Thanks, but it doesn't seem to change anything : I added 
> max_outgoing_migrations = 1
> migration_max_bandwidth = 5

well this is not going to make it any faster, quite the opposite:)
You need to play with the downtime setting (in UI or in vdsm.conf) to affect convergence in your constrained connectivity setup

There’s a lot more intelligence in oVirt 4.0 regarding this, so if it’s an option I would recommend to upgrade and change the migration policy to one of the new ones

Thanks,
michal

> in /etc/vdsm/vdsm.conf
> on my concerned host, but it still goes to 98% use of network and migration fail...I restart vdsmd.service but it doesn't seem to change anything. Any idea ?
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