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Karel_Bollen's avatar
Karel_Bollen
Level 3
12 years ago

Service group dependency

I have a 3 node cluster with VCS 6.0.1 and RHEL6 On the first two nodes by default different production applications are active and on the third node the acceptance applications are active. The a...
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business continuity
Cluster Server
  • mikebounds's avatar
    mikebounds
    12 years ago

    You need an offline local dependency so make Both production service group parent of child acceptance service group so you have:

    prod1_grp depends on accept_grp offline local

    prod2_grp depends on accept_grp offline local

    This means accept_grp must be offline on node 3 to be able to online or switch prod1_grp or prod2_grp to node3, so you will get a 'group dependency violation error' if you try to do this as the expectation is that if you manually switch or online prod1_grp or prod2_grp on node3, that you manually offline accept_grp first, BUT, if prod1_grp or prod2_grp fault and tries to switch to node3, then the service group dependency means VCS will automatically offlines accept_grp so that prod grp can online on node3 and in this instance if accept_grp can only run on node3, it will stay down. 

    Mike

g_lee's avatar
g_lee
Level 6
12 years ago

Karel,

As Mike points out, it is expected that you get the group dependency violation error if you manually try to switch the groups - the dependency will offline the acceptance group when the prod group faults and tries to failover (this is different to running hagrp -switch or hagrp -online manually).

To test you would need to manually trigger a fault in the one of prod groups, and see that it takes the accept group offline before bringing that prod group up on node3.

As mentioned in the earlier post, if you only had one prod group you could use offline local; as you have 2 prod groups you cannot make them both offline local as this is a known limitation (per 3rd link, "A configuration in which multiple child service groups are offline local" is not supported); so it may be worthwhile looking into the suggestions in Mike's second post to see if this meets your requirements (using Limits and Prerequisites in combination with online remote <soft|firm> dependencies).