Multiple VM migration (on maintenance)

[arc1]

Hi,
I have a question about migration of VMs.
If i put host into maintenance mode, VMs on that host are migrated one by one and it takes quite a bit of time to migrate all of them.
But if i do a manual migration, I can choose multiple (or all VMs) and when i click "migrate" all VMs start migration at the same time. That process is much faster than one by one migration.
Is there any particular reason for not migrating all VMs together on maintenance mode?

[DustinB]

Good question.

When you put a host into maintenance mode, that host then refuses any new VM workloads (either migrated or a new VM build).

If you don't put a host in maintenance mode, that host can then accept VM's to be migrated back to it, or to allow new VMs to be created on it.

As to why all VM's aren't migrated en masse I'm not sure, maybe someone from the Vates team can explain in more depth.

[olivierlambert]

It's because doing more at the same time on busy VM could lead to more suspend time from your VM perspective. There's a number you can change somewhere but I do not remember where (@BenjiReis might remember?)

[BenjiReis]

There's a evacuation-batch-size in /etc/xapi.conf that can be overridden (not edited directly in the file, see the warning in the header about this) by putting a new configuration file in /etc/xapi.conf.d/, to tell how many VMs to migrate at the same time when evacuating an host.

[Updated by Stormi to avoid letting think that it's OK to edit /etc/xapi.conf]

[Andrew]

@BenjiReis I added evacuation-batch-size = 4 to the end of /etc/xapi.conf and then did a xe-toolstack-restart but it did not change from only one at a time. What did I miss?

[Danp]

@Andrew Could that be one of the new options that only apply to XCP-ng 8.3 or later?