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Group dependencies

Cluster_Server
Level 3

‎09-10-2008 05:37 AM

Hi,

 

another group dependency question:

 

G1 is a parallel group and online on Server A and B

G2 is a failover group and online on Server B

 

G2 is depending from G1

 

In G1 there is only a mount resource, in G2 there is a application resource

 

When I umount the filesystem on server A nothing should happen, because G2 is online

on server B and the mount resource from G1 is also online on server B.

 

But unfortunately G2 fails because G1 fails.

 

My question:

Which group dependency must I choose, so that G2 only fails when mount resource fails

on the same side as G2?

 

Regards

Heinz

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2 REPLIES 2

Cluster_Server
Level 3

‎09-17-2008 09:45 AM

Hi Guys,

 

anyone here who has a similiar configuration as described in my first posting?

 

Regards

Heinz 

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Roger_Zimmerman
Level 4

‎10-28-2008 02:33 AM

Hi Cluster Server,

 

I'm afraid you made an major configuration failure. Group dependencies unfortunately work cluster global, not node local. That is, when G1 fails on one node, all dependent service groups on all nodes fail. The solution in your case is not to have group dependencies but the proxy mechanism.

 

In detail:

 

G1 is a parallel group with only the mount (maybe with the ressource name "Mount1" ). G1 is online on A and B. So far so good. (Be aware that this mount have to be an CFSfilesystem.)

 

G2 is a failover group and has in the bottom of the resource dependency tree a ressource (maybe with the name "Mount1Proxy" ) with a ressource type "Proxy". And this  Proxy ressource have an attribute that is namedTargetResName, and this attribute is to be filled with the name "Mount1". And all yourother application details are above this Proxy ressource and depend from this ressource. The big trick is now, the Proxy ressource is online, when the TargetResName is online and vice versa. If on the local Node the G1 group is failing (including a failure of the Mount1 ressource) then also the Mount1Proxy ressource is going offline and: there is your service group failover to the other node! And: if the G1 is failing on this node where G2 is offline, G2 is ignoring this, because G2 is NOT DEPENDING on G1, but the Proxy ressource is depending on the LOCAL ressource for your mount point. Bingo.

 

There is a short description of this mechanism including a sample in the Bundled Agents Reference Guide. Agent "Proxy".

 

Finally, the nickname is not that bad. My nickname is boring... :smileywink:

 

Hope this helps 

Roger

Message Edited by Roger Zimmermann on 10-28-2008 10:34 AM
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