[ClusterLabs] Offtopic - role migration

Vladislav Bogdanov bubble at hoster-ok.com
Tue Apr 18 13:50:26 EDT 2023

Btw, an interesting question. How much efforts would it take to support a 
migration of a Master role over the nodes? An use-case is drbd, configured 
for a multi-master mode internally, but with master-max=1 in the resource 
definition. Assuming that resource-agent supports that flow -
1. Do nothing.
2. Promote on a dest node.
3. Demote on a source node.

Actually just wonder, because may be it could be some-how achievable to 
migrate VM which are on top of drbd which is not a multi-master in 
pacemaker. Fully theoretical case. Didn't verify the flow in-the-mind.

I believe that currently only the top-most resource is allowed to migrate, 
but may be there is some room for impovement?

Sorry for the off-topic.


Ken Gaillot <kgaillot at redhat.com> 18 апреля 2023 г. 18:23:00 написал:

> On Tue, 2023-04-18 at 14:58 +0200, lejeczek via Users wrote:
>> Hi guys.
>> When it's done by the cluster itself, eg. a node goes 'standby' - how
>> do clusters migrate VirtualDomain resources?
> 1. Call resource agent migrate_to action on original node
> 2. Call resource agent migrate_from action on new node
> 3. Call resource agent stop action on original node
>> Do users have any control over it and if so then how?
> The allow-migrate resource meta-attribute (true/false)
>> I'd imagine there must be some docs - I failed to find
> It's sort of scattered throughout Pacemaker Explained -- the main one
> is:
> https://clusterlabs.org/pacemaker/doc/2.1/Pacemaker_Explained/html/advanced-options.html#migrating-resources
>> Especially in large deployments one obvious question would be - I'm
>> guessing as my setup is rather SOHO - can VMs migrate in sequence or
>> it is(always?) a kind of 'swarm' migration?
> The migration-limit cluster property specifies how many live migrations
> may be initiated at once (the default of -1 means unlimited).
> --
> Ken Gaillot <kgaillot at redhat.com>
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