| Section | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
[Figure] Online/Offline Sequence of Dependent Resources When Starting or Terminating a Group
...
define this dependency among resources, configure this link in the ‘Resource Dependency’ view.
[Figure] Dependency relationship
...
In MCCS, you can configure the dependency relationship of resources by using a tree.
From the above screen, we can find out about the dependency relationship among resources.
The network address resource as a parent depends on the NIC resource as its child. The application resource as a parent depends on the network address resource as its child.
MCCS performs a failover on a group basis. Thus, all the resources within a group should be connected in this dependency relationship and they need to be put into a single group before we can provide meaningful service.
If we set two resources as a parent and an child, we can see it as two vertical levels. The max level can be checked in the 'MaxDependencyLevel' value in the group attribute menu.
Link
[Figure] Setting Link
...
| Warning |
|---|
※ For linking process, first selected resource is parent resource and the one selected later is the child resource. |
Dependency Removal
[Figure] Setting Unlink
...
Many applications record data in a disk or storage. Thus, applications must depend on disks in the dependency relationship.
If you use the DB, you need to designate the disk to record data in. Thus, for the DB, you must set the dependency relationship where the DB as a parent depends on the disk as a child.
If a client needs an IP address to access the DB, you must set the network address as an child and the DB as a parent. Based on this dependency relationship, when a group goes online in MCCS, first check the network address resource and confirm whether the disk are unlocked properly before running the DB.
Thus the DB should be set to depend on both the network address resource and the disk resource.
We can provide the following configurations based on the dependency relationships discussed so far.
[Figure] Dependency of database application
...
Actions due to dependency
Online/Offline of the group is performed from bottom to top according to the dependency in case of online, and from top to bottom in case of offline.
Following are a few examples how MCCS manages the resources after dependency link among the resources when a resource is failed.
Attributes and state of resources are defined as the figure below.
[Figure] Resource State Information Charts
...
- Failure occurs from a resource on which critical resource depend.
[Figure] Example of Failure Occur 1
- As a failure is occurred at resource r2, resource r1 will be taken offline. (Since resource r1 depends on resource r2 which is failed, resource r1 may cannot be online properly.)
- Since resource r1 has critical attribute, resource r3 and a4 will be taken offline in order to failover the group.
- As a result, resource r2 is considered as failure and all resources in the group will be taken offline
Non-critical Resources
[Figure] Example of Failure Occur 2
...
RestartLimit is an attribute of the resource type. This value determines how many times the recovery will be attempted until it is finally confirmed that it is failure.
(Please refer to "6. Resource Type" for more details.)
[Figure] Example of Failure Occur 3
...