[PVE-User] Migration target node in case of shutdown

[PVE-User] Migration target node in case of shutdown

[Maximilian Hill]

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Hello,

how exactly does Proxmox VE determine the target node of a migration in
case of a shutdown?


Thanks,

Max

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Re: [PVE-User] Migration target node in case of shutdown

[Stefan Sterz]

Hello,

the target node is chosen by the node priority of the HA group that a
VM is in. You can read more about that in the manual [1]. Here is an
example: Assuming you have a three node cluster (node0, node1, node2)
and the HA group has the following priorities: node0:2, node1:1,
node2:0. A VM running on node0 will be moved to node1 and then node2
if each node fails one after another. If several nodes have the same
priority, VMs will be distributed evenly.

Best regards,
Stefan

[1]:
https://pve.proxmox.com/pve-docs/pve-admin-guide.html#ha_manager_groups

On 14.04.22 11:36, Maximilian Hill wrote:
> Hello,
> 
> how exactly does Proxmox VE determine the target node of a migration in
> case of a shutdown?
> >
> Thanks,
> 
> Max
> 
> 
> _______________________________________________
> pve-user mailing list
> pve-user@lists.proxmox.com
> https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-user

Re: [PVE-User] Migration target node in case of shutdown

[Maximilian Hill]

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Hello Stefan,

the reason I'm asking, is, that I ran into a case, in which the
priorities were all equal (not set), but all VMs were tried to migrate
from two nodes to the same node of a 8 node cluster.

This by itself wouldn't really be a problem, but qemu managed to
allocate all the memory for the VMs, so no migration failed to start.
Then the VMs used the memory and the OOM started to kill VMs and other
processes.

In this special case, we have a temporary workaround in place:
- No swap
- vm.overcommit_memory = 2
- vm.overcommit_ratio = 99

This of course is not a nice solution at all.


Best regards,
Max

On Thu, Apr 14, 2022 at 12:40:35PM +0200, Stefan Sterz wrote:
> Hello,
> 
> the target node is chosen by the node priority of the HA group that a
> VM is in. You can read more about that in the manual [1]. Here is an
> example: Assuming you have a three node cluster (node0, node1, node2)
> and the HA group has the following priorities: node0:2, node1:1,
> node2:0. A VM running on node0 will be moved to node1 and then node2
> if each node fails one after another. If several nodes have the same
> priority, VMs will be distributed evenly.
> 
> Best regards,
> Stefan
> 
> [1]:
> https://pve.proxmox.com/pve-docs/pve-admin-guide.html#ha_manager_groups
> 
> 

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