Migrations after updates

[acebmxer]

While testing the latest 8.3 updates (may have been happening before) I noticed my vms will migrate back over to host 1 when it come back online so both host are running equal ran/cpu usage (4 vms) 2 on each host. When i finish updating host 2 and it come back online i expect 2 of vms to migrate back to host2. They do not, but will if i manually migrate them.

My load balancer settings... Is this expected behavior or should i modify my settings?

[DustinB]

@acebmxer Using performance mode should migrate your VM's so all systems are equally "performant" the different modes are outlined here https://docs.xcp-ng.org/management/vm-load-balancing/

As to why your VMs not migrate, I would only be guessing - anyways my guess is that it only polls the system every so often and if your systems are performing well enough nothing gets moved...

[Greg_E]

This reminds me that I have some work to do on my policy, mostly for anti-affinity.

[florent]

ping @bastien-nollet

[Bastien Nollet]

Hi @acebmxer,

I think the reason for this is a feature we recently added that prevents VMs from moving back-and-forth between hosts. VMs now have a cooldown (default 30min) between 2 load-balancer-triggered migrations

Can you try to set the migration cooldown to 0 and tell us if it fixes this behaviour? (in the "Advanced" section of the load balancer configuration)

[acebmxer]

@Bastien-Nollet

I was playing around with the settings last night and the only way i could get behavior i was looking for was to set free memory limit.

I did try your suggestion this morning. I reconfigured settings back to those in screenshot. Applied your recommendation and then but host 2 in maintenance mode. waited a few minutes. Took out of maintenance mode and vms still sitting on host 1.

I dont seem to have this issue on my work production servers. I guess to little vms and to little load in the home lab. I think in the past i may not have noticed it as I would be doing some other work in a vm or two generating load.

Unless other have different recommendations i think having free memory set to half the host ram will keep this even. Are there any unforeseen issues i should be aware in this config for home lab?

I am used to VMware just spreading vms across all host evenly then shuffling around the load based off cpu accordingly.