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Composite data source

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hi~all:

I have 3 node,A,B&C,

If nodes A and B become unavailable, i want the applications restarted on node C,

So,i create a SHARED data source between A&B, and a MIRROR data source between B&C,

and then created a Composite data source Contains SHARED & MIRROR,

How to to execute the  sequence?MIRROR First? Or SHARED  have priority?

THANKS~

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ecervant
2 Iron

Re: Composite data source

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I do not believe the proposed configuration would work in the environment.  The Shared disk data source and the Mirror Data source both use the VincaMV filter driver to block access to the partition.  Using both data sources on the same partition may cause a conflict in the driver and potentially cause unexpected behavior with one of the data sources.

The concept of this configuration may not work either because there is no replication mechanism to Node C when the Resource group is running on Node A.  In the proposed configuration the Mirror Data source only replicates when the data source is attached to node B.  If the resource group is running on node A then it will only attach the shared disk and the C node partition will not be updated.

Typically the Composite data source is used with a local Shared Disk or mirror data source between nodes A and B.  A RepliStor data source will be used to replicate the data to node C and will only be enabled on the node which is currently running the local shared disk or mirror data source.  Here is an overview of the Composite data source:

Node A to Node B = Shared or mirror Data Source
Node A to Node C = RepliStor Data Source
Node B to Node C = RepliStor Data Source

So when the Shared Disk is attached to Node A it will also enable the RepliStor data source from node A to Node C.  When you failover to node B it will then enable the RepliStor Data source from node B to Node c.  With this configuration it will always replicate to the DR site regardless of which local node is running the resource group.

Please view the EMC AutoStart administrator's guide as the data source requires the configuration of environmental variables on top of selecting the individual data sources.  I hope this helps with your Composite data source configuration.

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tribicic
3 Argentium

Re: Composite data source

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I haven't actually tried it, but I'd say that the shared disk resource has to go online first in order for the mirroring to be able to access the volume.
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ecervant
2 Iron

Re: Composite data source

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I do not believe the proposed configuration would work in the environment.  The Shared disk data source and the Mirror Data source both use the VincaMV filter driver to block access to the partition.  Using both data sources on the same partition may cause a conflict in the driver and potentially cause unexpected behavior with one of the data sources.

The concept of this configuration may not work either because there is no replication mechanism to Node C when the Resource group is running on Node A.  In the proposed configuration the Mirror Data source only replicates when the data source is attached to node B.  If the resource group is running on node A then it will only attach the shared disk and the C node partition will not be updated.

Typically the Composite data source is used with a local Shared Disk or mirror data source between nodes A and B.  A RepliStor data source will be used to replicate the data to node C and will only be enabled on the node which is currently running the local shared disk or mirror data source.  Here is an overview of the Composite data source:

Node A to Node B = Shared or mirror Data Source
Node A to Node C = RepliStor Data Source
Node B to Node C = RepliStor Data Source

So when the Shared Disk is attached to Node A it will also enable the RepliStor data source from node A to Node C.  When you failover to node B it will then enable the RepliStor Data source from node B to Node c.  With this configuration it will always replicate to the DR site regardless of which local node is running the resource group.

Please view the EMC AutoStart administrator's guide as the data source requires the configuration of environmental variables on top of selecting the individual data sources.  I hope this helps with your Composite data source configuration.

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jschrade1
2 Iron

Re: Composite data source

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I certainly agree with Emiliano's comments.  The vincamv.sys deiver would block access to the Shared drive on node B whenever the Shared drive is attached to node A.  That means that Node B would not have access to the Shared disk and could not Mirror the disk to node C.  As mentioned, the Composite DataSource was created specifically for use with the RepliStor DataSource.  The Shared Disk and Mirrored DataSources share the functionality of the partitioin locking that is provided by the vincamv.sys filter driver.
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tribicic
3 Argentium

Re: Composite data source

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You are both right of course.... I never had a pleasure to use composite data source but whenever it is discussed it mentions Replistor as one of the components.
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