Thanks I think I got it now. I can adjust my cluster policy accordingly ----- Original Message ----- From: "Gilad Chaplik" <gchaplik@redhat.com> To: "Jiri Moskovcak" <jmoskovc@redhat.com> Cc: "Maurice James" <mjames@media-node.com>, "users" <users@ovirt.org> Sent: Monday, June 30, 2014 9:20:31 AM Subject: Re: [ovirt-users] Spam Cluster Polcies ----- Original Message -----
From: "Jiri Moskovcak" <jmoskovc@redhat.com> To: "Gilad Chaplik" <gchaplik@redhat.com> Cc: "Maurice James" <mjames@media-node.com>, "users" <users@ovirt.org> Sent: Monday, June 30, 2014 4:19:06 PM Subject: Re: [ovirt-users] Spam Cluster Polcies
On 06/30/2014 03:11 PM, Gilad Chaplik wrote:
----- Original Message -----
From: "Jiri Moskovcak" <jmoskovc@redhat.com> To: "Gilad Chaplik" <gchaplik@redhat.com>, "Maurice James" <mjames@media-node.com> Cc: "users" <users@ovirt.org> Sent: Monday, June 30, 2014 3:57:29 PM Subject: Re: [ovirt-users] Spam Cluster Polcies
On 06/30/2014 01:53 PM, Gilad Chaplik wrote:
----- Original Message -----
From: "Maurice James" <mjames@media-node.com> To: "users" <users@ovirt.org> Sent: Friday, June 27, 2014 1:20:23 AM Subject: [ovirt-users] Spam Cluster Polcies
Can someone explain the cluster policies to me? The explanation at http://www.ovirt.org/Features/Even_VM_Count_Distribution is not quite clicking for me.
* HighVMSCount - Maximum VM limit. Exceeding it qualifies the host as overloaded. ( Understood )
minimal #vms on host to enable the module (i.e worst host should have more than HighVMSCount vms).
* MigrationThreshold - defines a buffer before we start migrating VMs from the host ( Not quite grasping. If my High limit is 5 does this mean that it will only begin to move VMs when the count reaches 10? )
don't think that there's any relation with "HighLimit". It means that migration will happen only if there is a difference of X vms or more between worst host (source host) to destination host.
let say that you have 2 hosts. one has 10 vms and the second 8. if the threshold is 3, no migration will happen (10-8 !> 3).
- exactly
* SPMVMCountGrace - defines how many slots for VMs should be reserved on SPM hosts (the SPM host should have less load than others, so this variable defines how many VM less it should have) ( Does this mean that if I have a host with only 3 VMs the SPM will 3 VMs minus the SpmWmGrace? Or is this HighVmCount minus SpmVmGrace count?)
you're right, the SPM host will have current + grace VMs in terms of module calculations. I think that this is problematic, it is likely to be selected as worst host candidate and that's not the wanted behavior iiuc imo, we should subtract (-) in overloaded hosts and add (+) in underutilized.
- I think it's correct as it is, if the SpmVmGrace+currentVms > HighVmCount it is overutilized and should be freed if possible.
not sure I understand, let's take an example 2 hosts: spm: 8 #vms, hsm: 8 #vms. SPMVMCountGrace = 2. in this case the 'worst' host will be the SPM... shouldn't we deduct 2 from spm and not add? we want less noise there.
- that's correct, the SPM will be marked as overutilized and the engine will try to find a host to migrate some vms from the SPM. The SpmGrace is not about lowering the noise it's about keeping the host less utilized by running less VMs on it (which will also lower the noise, because it will give the SPM host worse score when looking for target to migrate to)
got it, thanks :-)
--J
--J
@Jirka?
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