[ClusterLabs] Antw: [EXT] Re: Preferred node for a service (not constrained)

[Reid Wahl]

On Thu, Dec 3, 2020 at 5:09 AM Strahil Nikolov <hunter86_bg at yahoo.com> wrote:
>
> The problem with infinity is that the moment when the node is back - there will be a second failover. This is bad for bulky DBs that power down/up more than 30 min (15 min down, 15 min up).

That's true for the general case. In Petr's case, he has explicitly
said that he wants that behavior.

> Best Regards,
> Strahil Nikolov
>
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> В четвъртък, 3 декември 2020 г., 10:32:18 Гринуич+2, Andrei Borzenkov <arvidjaar at gmail.com> написа:
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> On Thu, Dec 3, 2020 at 11:11 AM Ulrich Windl
> <Ulrich.Windl at rz.uni-regensburg.de> wrote:
> >
> > >>> Strahil Nikolov <hunter86_bg at yahoo.com> schrieb am 02.12.2020 um 22:42 in
> > Nachricht <311137659.2419591.1606945369370 at mail.yahoo.com>:
> > > Constraints' values are varying from:
> > > infinity which equals to score of 1000000
> > > to:
> > > - infinity which equals to score of -1000000
> > >
> > > You can usually set a positive score on the prefered node which is bigger
> > > than on the other node.
> > >
> > > For example setting a location constraint like this will prefer node1:
> > > node1 - score 10000
> > > node2 - score 5000
> > >
> >
> > The bad thing with those numbers is that you are never sure which number to
> > use:
> > Is 50 enough? 100 Maybe? 1000? 10000? 100000?
> >
>
> +INFINITY score guarantees that resource will always be active on
> preferred node as long as this node is available but allow resource to
> be started on another node if preferred node is down.
> ...
> > > I believe I used the value infinity, so it will prefer the 2nd host over
> > > the 1st if at all possible.  My 'pcs constraint':
> > >
>
> And this was the very first answer to this question.
>
>
> > > [root at 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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-- 
Regards,

Reid Wahl, RHCA
Senior Software Maintenance Engineer, Red Hat
CEE - Platform Support Delivery - ClusterHA