[Pacemaker] migrate_from/migrate_to for Stateful RAs

[Florian Haas]

Andrew,

does the CRM/PE allow for resource migration with
migrate_to/migrate_from for Master/Slave RAs? This would imply that at
some point (during migration) multiple instances would be in the Master
role, and master-max would be ignored (or implicitly incremented by 1)
but while *not* migrating, master-max would be enforced.

And in addition to that, what are the implications of initiating
migration for a set of resources joined via colocation constraints, all
the resources of which implement migrate_from and migrate_to and are set
to "allow-migrate=1"?

To sum up, would the CRM/PE allow something like this:

- migration-capable drbd resource
- VirtualDomain resource (already migration-capable)
- colocation constraint making VirtualDomain dependent on drbd's Master role
- "crm resource migrate <VirtualDomain resource>"
- now do drbd migrate_to first, then VirtualDomain
migrate_to/migrate_from, and *now* drbd migrate_from?

I realize this probably sounds like I'm totally off my rocker, but would
this be feasible in any way?

Cheers,
Florian



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