[Pacemaker] Migration of "lower" resource causes dependent resources to restart

Vladislav Bogdanov bubble at hoster-ok.com
Thu Mar 29 02:43:55 EDT 2012

29.03.2012 09:35, Andrew Beekhof wrote:
> On Thu, Mar 29, 2012 at 5:28 PM, Vladislav Bogdanov
> <bubble at hoster-ok.com> wrote:
>> Hi Andrew, all,
>> Pacemaker restarts resources when resource they depend on (ordering
>> only, no colocation) is migrated.
>> I mean that when I do crm resource migrate lustre, I get
>> LogActions: Migrate lustre#011(Started lustre03-left -> lustre04-left)
>> LogActions: Restart mgs#011(Started lustre01-left)
>> I only have one ordering constraint for these two resources:
>> order mgs-after-lustre inf: lustre:start mgs:start
>> This reminds me what have been with reload in a past (dependent resource
>> restart when "lower" resource is reloaded).
>> Shouldn't this be changed? Migration usually means that service is not
>> interrupted...
> Is that strictly true?  Always?

This probably depends on implementation.
With qemu live migration - yes.
With pacemaker:Dummy (with meta allow-migrate="true") probably yes too...

> My understanding was although A thinks the migration happens
> instantaneously, it is in fact more likely to be pause+migrate+resume
> and during that time anyone trying to talk to A during that time is
> going to be disappointed.

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