Enable debug logging on nova-scheduler, you will see how the winner is picked. I had the same issue before, caused by the build-failure weigher enabled by default. setting build_failure_weight_multiplier to 0 resolved issue for me. Instances are balanced by weighers (compute and memory) as expected. shuffle_best_same_weighed_hosts and host_subset_size are not necessary, unless it's required by certain cases. Tony ________________________________________ From: Laurent Dumont <laurentfdumont@gmail.com> Sent: February 15, 2022 12:54 PM To: Franck VEDEL Cc: openstack-discuss Subject: Re: [kolla-ansible][nova]Problem with distribution of instance on servers There are two settings we've tweaked in the past in Nova. shuffle_best_same_weighed_hosts --> Allow more spreading in the case of computes with the exact same specs/weights. host_subset_size --> Helps with concurrent requests to get different hosts Before that, we saw the same behavior with Openstack stacking VM on single computes. It still respects anti-affinity, but I don't see a good reason to not spread as a default. Changing these two was enough to allow our spread to get a little better. On Tue, Feb 15, 2022 at 11:19 AM Franck VEDEL <franck.vedel@univ-grenoble-alpes.fr<mailto:franck.vedel@univ-grenoble-alpes.fr>> wrote: Hello, I seem to have a problem that I hadn't seen. I have 3 servers for my openstack, built with Kolla-ansible, I'm in Victoria version. I had simply put the 3 servers in the [compute] part of the multinode file, at first it worked, but for some time all the VMs are placed on server 1. The 3 servers are operational, identical. here are 3 screenshots to show it. (on the images, the instances on servers 2 and 3 are present because it worked correctly, but no more instances are created on these servers now) [cid:17eff2778356f37a4481] [cid:17eff277835e47aa83c2] [cid:17eff2778356f53d34a3] I tried to understand how the instances are distributed on the servers, but in my case, I don't understand why none are assigned to the 2nd and 3rd server. How to find the problem? It should be nova-scheduler . Do you have to do anything special? Go see if a parameter has a bad value? Thanks in advance if you can help me. Franck VEDEL
