load balance, density. Doesnt seem to be working

olivierlambert

Yes but there's likely a minimal load threshold where it could be group on less machines I don't remember the numbers though, @Bastien-Nollet will take a look, it's been a while since nobody asked for density mode

Tristis Oris

probably, documentation not very correct.

Bastien Nollet

Hi,

There are several things that can prevent the density plan from regrouping your VMs to only one host :

if your hosts can't be restarted
if some of the VMs on your host don't support pool migration
if your host doesn't have enough memory or CPU to correctly handle all your VMs
if the migration would go against anti-affinity rules (but according to your screenshot you haven't defined anti-affinity tags, so this can't happen)

Though, I just noticed that there is probably an issue with the CPU and memory threshold values, which would lead to trying to do migrations even if they are not possible in terms of memory or CPU. I will investigate on that, and test that the density plan is still working correctly for us.

Bastien Nollet

@manilx said in load balance, density. Doesnt seem to be working:

@Tristis-Oris They don't. Nothing happens.

Edit: Also "In this mode, you can choose to shutdown unused (and compatible) hosts" don't see where to set this.

You actually don't need to set this, it is not configurable. Host are shut down when all their VMs have been migrated.
Thank you for pointing that out, we need to update the doc on this.

manilx

@Bastien-Nollet All the points you pointed out are OK here and should not be a hindrance.
But this is definitely not working here.

Bastien Nollet

@manilx Ok, then I'll have to investigate on this to see if the density plan is still working properly for us, or if there are other things that may be preventing it from working for you.

olivierlambert

I'm pretty sure the reason is very likely because the host can't be restarted automatically. For that, you need to enable host-set-power-on-mode.

manilx

@olivierlambert How do I test this to check this?

olivierlambert

Old article but probably still relevant: https://xen-orchestra.com/blog/how-to-use-wake-on-lan-on-xenserver-6-2/

manilx

@olivierlambert Thx, will check this out.