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For various reasons beyond our control, a critical service running on a particular machine must communicate to another machine via a preset and fixed IP address.

Both machines run Windows Server 2008 Standard and both are joined to the same Active Directory domain. The target machine also hosts various other services.

At issue is how to handle a scenario where the target machine fails. The plan is to have a clone of the target machine in cold stand-by. When the target machine fails, the cloned machine will be manually powered up with the expectation that operation resumes as normal.

Both the "target" machine and it's inactive clone will be configured to have the same IP address & hostname.

Is this feasible? Can Active Directory manage this scenario without special configuration?

Many Thanks.

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It might be better to investigate if you can set up a cluster, use the fixed IP as the cluster VIP, and run the application under the cluster. If it runs as an actual Windows service, this might be easy. –  mfinni Sep 22 '11 at 19:33
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3 Answers

up vote 1 down vote accepted

1) If you want to go this way, be sure to actually clone the machine, and not to just set up another one with the same name and configuration. Otherwise the domain will definitely not welcome the replacement machine.

2) If the standby machine is disconnected from the domain for more than 30 days, the active machine will reset its computer account's password, so the standby machine, when powered up, will not be able to access the domain. This can be fixed by removing it from the domain and joining it again.

3) If your service uses Active Directory for anything other than authentication (things like populating an internal database from directory data, or writing anything to AD and expecting it to be still there the next time), the replacement machine will get out of sync; the same, of course, is true if it exchanges data with any other machine on the network.

Apart from these points, everything should work fine...

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Many thanks. I wonder if your points 2 & 3 can be mitigated somewhat if we disconnect the machines from the AD. Or perhaps there's a standalone mode? Somewhere between a domain member and a workgroup? –  VikenY Sep 22 '11 at 23:41
    
No, either a machine is a domain member, or it isn't; but a domain re-join will happily fix point 2. –  Massimo Sep 23 '11 at 8:31
    
About point 3: this really depends on what your application actually does... –  Massimo Sep 23 '11 at 8:32
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Basically, you are doing an image backup and a "restore" on different hardware in a failover scenario. As long as the machine in question is not a domain controller and does not have any services which sync their state with AD, it should be fine.

Otherwise, you should check with Microsoft and the vendor of any 3rd party service syncing with AD for a supported backup solution. For details on implications with incorrect AD backup/restore procedures see KB 875495.

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I can see Licensing being a potential snag. If you ever have to use this server for this, I would login and run "slui" from a cmd prompt.

If you have a KMS in your org, then it may consume another license. This scenario would be a good use of a P2V so you don't have a physical asset sitting idle.

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