[ClusterLabs] Antw: Re: Antw: [EXT] staggered resource start/stop

[Ken Gaillot]

On Mon, 2021-03-29 at 13:01 +0200, Ulrich Windl wrote:
> > > > Reid Wahl <nwahl at redhat.com> schrieb am 29.03.2021 um 12:47 in
> > > > Nachricht
> 
> <CAPiuu9-R+ywB7h7zp83pcVUL4zV2vdaUD0Fyjq3NRHLpVrYRbw at mail.gmail.com>:
> > On Mon, Mar 29, 2021 at 3:35 AM Ulrich Windl <
> > Ulrich.Windl at rz.uni-regensburg.de> wrote:
> > 
> > > > > > d tbsky <tbskyd at gmail.com> schrieb am 29.03.2021 um 04:01
> > > > > > in Nachricht
> > > 
> > > <
> > > CAC6SzHLi0ufVhE3RM57e2V=t_mOmL5ECX8AY3gtcfGmOfKDaxg at mail.gmail.com
> > > >:
> > > > Hi:
> > > >    since the vm start/stop at once will consume disk IO, I want
> > > > to
> > > > start/stop the vm
> > > > one‑by‑one with delay.
> > > 
> > > I'm surprised that in these days of fast disks and SSDs this is
> > > still an
> > > issue.
> > > Maybe don't delay the start, but limit concurrent starts.
> > > Or maybe add some weak ordering between the VMs.
> > > 
> > 
> > kind=Serialize does this. It makes the resources start
> > consecutively, in no
> > particular order. I added the comment about ocf:heartbeat:Delay
> > because D
> > mentioned wanting a delay... but I don't see why it would be
> > necessary, if
> > Serialize is used.
> 
> This problem made me think of: Does there exist a mechanism for the
> rather new
> tag mechanism to impose a concurrency limit per tag? So the VMs could
> be tagged
> as "VM", and if you limit concurrency for tag "VM" to 1 or 2, you'd
> be done,
> not limiting other resources...

Serialize turns concurrency on/off rather than a number of concurrent
actions, but yes, tags can be used in resource sets, so you could
create a Serialize constraint using a resource set with a tag.

> And still the resources could start in the order the cluster thinks
> it's
> best...
> 
> Regards,
> Ulrich
> 
> > 
> > 
> > > > 
> > > >     search the email‑list I found the discussion
> > > > https://oss.clusterlabs.org/pipermail/pacemaker/2013‑August/043128.html 
> > > > 
> > > >     now I am testing rhel8 with pacemaker 2.0.4. I wonder if
> > > > there are
> > > > new methods to solve the problem. I search the document but
> > > > didn't
> > > > find new parameters for the job.
> > > > 
> > > >     if possible I don't want to modify VirtualDomain RA which
> > > > comes
> > > > with standard rpm package. maybe I should write a new RA which
> > > > stagger
> > > > the node utilization. but if I reset the node utilization when
> > > > cluster
> > > > restart, there maybe a race condition.
> > > > 
> > > >      thanks for help!
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> > 
> > 
> > -- 
> > Regards,
> > 
> > Reid Wahl, RHCA
> > Senior Software Maintenance Engineer, Red Hat
> > CEE - Platform Support Delivery - ClusterHA
> 
> 
> 
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-- 
Ken Gaillot <kgaillot at redhat.com>