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

[Ulrich Windl]

>>> 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...
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