ServiceNow Discovery: MID Server Clusters
Introduction
I am often asked for recommendations around how to deploy MID Servers without context of the environment. And it is hard to give sound recommendations without context. However…
I personally hate giving the answer ‘it depends’ as much as I hate being at the receiving end of it.
But here is one thing I can confidently recommend across ALL ServiceNow MID Server Deployments.
MID Server Clusters
Creating MID Server Cluster takes only a few taps and clicks.
Navigate to: MID Server > Clusters > New
Enter the Cluster Name and Select Type = ‘Load Balance’ and save the Record
Finally, remember to use the MID Server Cluster in the Schedule
Note that MID Server Clusters are not captured in Update Sets and need to be manually migrated (via XML) across the ServiceNow Instances. But once created (and synced across all the environments), any future migrations for Discovery Schedules are error free.
Reason: Unlike the MID Server, the sys_id of the MID Server Cluster remains the same across your instances.
Do this every time…
Always use MID Server Clusters… it is as simple as that.
While it is more intuitive to use MID Server Clusters when you have more than one MID Server, configure MID Server Clusters, even when you currently have only one MID Server.
Always use a Load Balanced Cluster vs a Fail Over Cluster. Load Balancing does Fail Over. And to offset the need for Fail Over, choose an appropriate MID Server Architecture instead.
Ensure the MID Server Design is sound and the MID Server Hosts in the Cluster have similar configurations.
Don’t assign a MID Server to more than one Cluster.
We also recommend clustering non-Prod MID Servers the same way we Cluster Prod MID Servers. This is for Design Validation as well as Performance Validation of Discovery in non-Prod, so you know exactly what to expect in Prod, after migration.
Conclusion
At this point, I often get questions on Behaviors, Functionalities and Capabilities.
I personally am not a fan of first starting with Behaviors, Functionalities and Capabilities. While, in concept, the features have merit, it may unnecessarily complicate the MID Server deployment and subsequent maintenance.
You will be pleasantly surprised with what you can achieve with MID Server Clusters.
