use of service group

[Arun_K]

What is the use of service gp in cluster?

What if i dont create it?

[mikebounds · Accepted solution]

A service group is a container of resources which moves the resources as one unit from node to another.  Without a service group, you can't move resources from one node to another so the cluster would not be doing anything !

Mike

[Arun_K]

I am new to this.

we can have how many service group?

if we have 2 resources under a service gp,then both will be a one unit?what this means?

[mikebounds]

I don't think there is a fixed limit to the number of service groups - this is really dependent on the CPU of your server, but I have configured clusters with 100+ service groups.

Example of resources are:

• Diskgroup (import and deport diskgroups)
• Mount (mount and umount filesystems)
• IP (plumb and unplumb and IP address)
• Application (start and stop your application)

So to move your application from one node to another you need to group the resources the application needs, like Diskgroup, mount and IP and the Application processes, so that they move over as one unit (you can't move the App without its storage)

You create a second service groups if you have another application which can move from one node to another independent of the other (it does not have to run on the same node)

Mike

[arangari]

Mike has already explained the service group.

In Nutshell:

1. Service group is set of software programs or representation of hardware components, together called as 'resource' in VCS terminonogy. These resources may have some inter-dependency for their correct working.

2. The service group will give a full service or part of service. 

3. The resources, although can be present on the system, can not be presented to VCS policy engine without a service group which acts as container. 

4. The resources are monitored for their 'up' status as per their properties, by agents written specifically for those programs/components.

5. The VCS policy engine, takes action on resource, however any failover across nodes is done only at service group level. Thus service group becomes very important object in VCS.

6. One can have as many resources per service groups, and as many service groups per cluster. The CPU and Memory available for process will impose restrictions on it. The soft-limit (which can be changed) for service group is 200, and for resources it is 5000. 

[Arun_K]

Service group may have may resources.But it willl be consider as a single entity?

Service group will be online only at one node at a time?

[mikebounds]

As single service group will normally have more than one resource - example it may contain 6 resources as shown below:

By default a service group is a failover service group so it can only run on one node at a time, but if you create a service group with service group attirbute Parallel=1, then this allows service group to run on more than one node at a time, so you can run parallel applications like Oracle RAC.

Mike

[Arun_K]

We have 3 service gp in our environment.

What is that for.

nbu_group

aptare_agent

cluster_service

[mikebounds]

Service groups can be called anything, but as a guess:

nbu_group - contains NBU resources

aptare_agent - contains Aptare resources

cluster_service - contains Cluster managent services (this may be just an IP, or could contain notification resource).

So this means for instance that NBU fails over independently of Aptare (if no SG dependencies have been defined), so sometimes they may be on the same node and sometimes on different nodes.

Mike

[arangari]

Arun,

You may want to refer to the documents for more details about the dependency etc, failover behaviors and many more features of VCS. 

[Marianne]

For some or other reason this user keeps on posting the same questions using different names:

https://www-secure.symantec.com/connect/forums/how-see-what-service-group-contains

https://www-secure.symantec.com/connect/forums/cluster-2

https://www-secure.symantec.com/connect/forums/cluster-query

And we keep on giving the same answers and keep on referring to documentation....  

*** Moved post to Cluster Server forum ***

[Arun_K]

@Mike:Why we freeze aptare agent then?Use of aptare service gp?

[Yasuhisa_Ishika]

I'm not sure why you freeze the apature  group. Ask who tells you need to freeze it.

Or have a look on this page and think why you need to freeze it.

https://sort.symantec.com/public/documents/vcs/6.0/linux/productguides/html/vcs_admin/ch06s12s06.htm