On 2020-11-30 23:21, Petr Bena wrote:
Hello,
Is there a way to setup a preferred node for a service? I know how to
create constrain that will make it possible to run a service ONLY on
certain node, or constrain that will make it impossible to run 2
services on same node, but I don't want any of that, as in
catastrophical scenarios when services would have to be located
together
on same node, this would instead disable it.
Essentially what I want is for service to be always started on
preferred
node when it is possible, but if it's not possible (eg. node is down)
it
would freely run on any other node, with no restrictions and when node
is back up, it would migrate back.
How can I do that?
I do precisely this for an active/passive NFS/ZFS storage appliance
pair.
One of the VSA has more memory and is less used, so I have it set to
prefer
that host.
https://clusterlabs.org/pacemaker/doc/en-US/Pacemaker/1.1/html/Clusters_from_Scratch/_prefer_one_node_over_another.html
I believe I used the value infinity, so it will prefer the 2nd host over
the 1st if at all possible. My 'pcs constraint':
[root@centos-vsa2 ~]# pcs constraint
Location Constraints:
Resource: group-zfs
Enabled on: centos-vsa2 (score:INFINITY)
Ordering Constraints:
Colocation Constraints:
Ticket Constraints:
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