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tbruheim1967Flag for Norway asked on

What happens if a Domino ICM server is down?

Problem. I`ve got 2 Lotus Domino servers in a cluster. Regardless how good ICM is developed, how in the world is a browser able to find out on its own, how to use another IP adress if one Domino server goes down? Yes a mail server is handled by MX records, but there is none MX like records for "a-records or cnames" in a DNS server that I am aware of. In linux we have a cache server in front. Cache servers can determine an alternate server back end.

As far I can see this may only work if we use an ICM serverice installed in front of a Domino cluster. Am I right about this folks?

Best regards Tor Bruheim
Lotus IBM

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tbruheim1967

8/22/2022 - Mon
doninja

The ICM server is doing the same job as the Linux cache server in determining which domino server is available or busy etc. Both ICM and Linux cache have same issue if the box is down so you need to ensure it is on the most reliable system possible.

To provide best high availability you need total network access so you can have machines fail-over to the public IP address or have them use some IP level load balancing.

If you don't have that level of network access then you could be able to modify the DNS record for the ICM server and have it on a very low TTL so that clients will contact the DNS server frequently.  
The ICM service can be placed on multiple clustered servers and the DNS points at the current ICM. a monitoring system would change the DNS entry if primary ICM is unavailable.
ASKER
tbruheim1967

Thank you very much. You verified very important topics for me. The thing that got me confused was the Lotus Domino manual. It seems that the Domino Administrator help suggest the possibility to use 2 ICP servers. I have attached 2 help sections from the Domino Help database regarding ICM to describe this topic:
Example of multiple ICMs inside the clusterExample of multiple ICMs outside the cluster
ASKER
tbruheim1967

I've requested that this question be closed as follows:

Accepted answer: 0 points for tbruheim1967's comment #37719234

for the following reason:

According to the manual the solution from experts-exchange is not complete, but only partial. The manual from Lotus Domino must be taken into consideration before we end this thread.
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doninja

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ASKER
tbruheim1967

Thank you very much. This was very useful. This was the exact answer I was looking for. It has dawn on me that an Ip sprayer will be a better solution in my case. I cannot rely 100 percent on this solution because it has weaknesses. Your answer put me on the right track. Thank you very much. Your solution was 100 percent correct to my questions.