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Oracle Solaris Cluster
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August 7, 2014
HA-LDOM live migration in Oracle Solaris Cluster 4.2
Most
Oracle Solaris Cluster resource types clearly separate their stopping and starting
actions. However, the HA-LDom (HA Logical Domain / HA for Oracle VM for SPARC data
service) agent has a capability of performing live migration, in
which an entire switchover of the resource is performed while the
cluster framework is stopping the resource. Suppose that the LDom
resource starts out on node A and the administrator executes a
switchover to node B. While the cluster framework is stopping the
resource on node A, LDom live migration is actually migrating the
LDom from node A to node B.
The
problem (which previously existed) with this approach arose if
another resource group declared a strong negative (SN) affinity for
the LDom resource's group or if load limits were in use. The LDom
is actually migrating onto the target node before the cluster
framework knows that it has started there, so the cluster framework
will not have had a chance to evict any resource group(s) due to
strong negative affinities or load limits. There will be an interval
of time in which the hard loadlimit or strong negative affinity will
be violated. This may cause overload of the node, and consequent
failure of the LDom live migration attempt.
With
Oracle Solaris Cluster 4.2 we eliminate the above said problem by
providing a mechanism in the cluster framework by which excess
workload can be migrated off of the target node of the switchover
before executing the live migration of the LDom. This is accomplished
by making use of the following two enhancements:
-
A
new resource property Pre_evict which ensures seamless live
migration of LDom. The Pre_evict property allows the cluster
framework to move excess workload off of the target node before the
switchover begins, which then allows the live migration to succeed
more often. -
A
new scha_resourcegroup_get query tag SCHA_TARGET_NODES which
allows a data service to perform the live migration by informing it
of the target node to be used for the migration.
For
the convenience of the users / administrators, the HA-LDom agent in
Oracle Solaris Cluster 4.2 has the Pre_evict set to True by default
and the agent is enhanced to take advantage of these new API
(Pre_evict and SCHA_TARGET_NODES query) features.
For
more information, refer the following links
-
pre-evict
resource property: -
SCHA_TARGET_NODES
query:
- Harish Mallya
Oracle Solaris Cluster