[Pacemaker] Migrating VMs that depend on other VMs

Lindsay Todd rltodd.ml1 at gmail.com
Mon May 13 12:28:17 EDT 2013

Folks: On my cluster built on SL6.4, I need to deploy some VMs that depend
on other VMs:

   - db0 has no dependendencies
   - ldap01,ldap02 require db0 to be running -- ordering constraint, but no
   collocation (other than we'll use a collocation constraint to recommend
   ldap01, ldap02 run on different physical hosts)
   - bq01, bq02 depend on at least one of ldap01, ldap02 running

At this point, I've got a test arrangement corresponding to only the db01
and ldap01 resources being deployed, but it is enough to expose a problem...

The constraints themselves are quite simple.  The trouble arises when we
try to migrate VMs.  As the "Pacemaker Configuration Explained" manual
states: "The resource must not, directly or indirectly, depend on any
primitive or group resources."  What is the reason for this restriction?
Sure enough, I can't migrate ldap01.  I can migrate db01 successfully,
though it does force a stop/start on ldap01 (though that is really
unnecessary, since network connections would have been preserved).

So is there a way to:

   - At least get the bq01, bq02 VMs able to migrate, though they depend on
   other VMs?
   - Be able to get the ldap01,ldap02 VMs to migrate, without forcing the
   bq01,bq02 VMs to stop/start (unless both get stopped the restarted)?
   - Be able to get the db01 resource to migrate, without forcing the other
   dependents to stop/start, unless it is actually stop/started?


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