[ClusterLabs] Antw: [EXT] Re: Order set troubles

[Reid Wahl]

FWIW we have this KB article (I seem to remember Strahil is a Red Hat
customer):
  - How do I configure SAP HANA Scale-Up System Replication in a Pacemaker
cluster when the HANA filesystems are on NFS shares?(
https://access.redhat.com/solutions/5156571)

I can't remember if there was some valid reason why we had to use an
attribute resource, or if we simply didn't think about the sequential=false
require-all=false constraint set approach when planning this out.

On Thu, Mar 25, 2021 at 3:39 AM Strahil Nikolov <hunter86_bg at yahoo.com>
wrote:

> OCF_CHECK_LEVEL 20
> NFS sometimes fails to start (systemd racing condition with dnsmasq)
>
> Best Regards,
> Strahil Nikolov
>
> On Thu, Mar 25, 2021 at 12:18, Andrei Borzenkov
> <arvidjaar at gmail.com> wrote:
> On Thu, Mar 25, 2021 at 10:31 AM Strahil Nikolov <hunter86_bg at yahoo.com>
> wrote:
> >
> > Use Case:
> >
> > nfsA is shared filesystem for HANA running in site A
> > nfsB is shared filesystem for HANA running  in site B
> >
> > clusterized resource of type SAPHanaTopology must run on all systems if
> the FS for the HANA is running
> >
>
> And the reason you put NFS under pacemaker control in the first place?
> It is not going to switch over, just put it in /etc/fstab.
>
> > Yet, if siteA dies for some reason, I want to make SAPHanaTopology to
> still start on the nodes in site B.
> >
> > I think that it's a valid use case.
> >
> > Best Regards,
> > Strahil Nikolov
> >
> > On Thu, Mar 25, 2021 at 8:59, Ulrich Windl
> > <Ulrich.Windl at rz.uni-regensburg.de> wrote:
> > >>> Ken Gaillot <kgaillot at redhat.com> schrieb am 24.03.2021 um 18:56 in
> > Nachricht
> > <5bffded9c6e614919981dcc7d0b2903220bae19d.camel at redhat.com>:
> > > On Wed, 2021‑03‑24 at 09:27 +0000, Strahil Nikolov wrote:
> > >> Hello All,
> > >>
> > >> I have a trouble creating an order set .
> > >> The end goal is to create a 2 node cluster where nodeA will mount
> > >> nfsA , while nodeB will mount nfsB.On top of that a depended cloned
> > >> resource should start on the node only if nfsA or nfsB has started
> > >> locally.
> >
> > This looks like ad odd design to me, and I wonder: What is the use case?
> > (We are using "NFS loop-mounts" for many years, where the cluster needs
> the
> > NFS service it provides, but that's a different design)
> >
> > Regards,
> > Ulrich
> >
> >
> >
> > >>
> > >> A prototype code would be something like:
> > >> pcs constraint order start (nfsA or nfsB) then start resource‑clone
> > >>
> > >> I tried to create a set like this, but it works only on nodeB:
> > >> pcs constraint order set nfsA nfsB resource‑clone
> > >>
> > >> Any idea how to implement that order constraint ?
> > >> Thanks in advance.
> > >>
> > >> Best Regards,
> > >> Strahil Nikolov
> > >
> > > Basically you want two sets, one with nfsA and nfsB with no ordering
> > > between them, and a second set with just resource‑clone, ordered after
> > > the first set.
> > >
> > > I believe the pcs syntax is:
> > >
> > > pcs constraint order set nfsA nfsB sequential=false require‑all=false
> > > set resource‑clone
> > >
> > > sequential=false says nfsA and nfsB have no ordering between them, and
> > > require‑all=false says that resource‑clone only needs one of them.
> > >
> > > (I don't remember for sure the order of the sets in the command, i.e.
> > > whether it's the primary set first or the dependent set first, but I
> > > think that's right.)
> > > ‑‑
> > > Ken Gaillot <kgaillot at redhat.com
> > >
> > >
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-- 
Regards,

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