Failover Cluster core resource

Question

Failover Cluster core resource

Robert Ditusa 1

Hello I currently have a windows failover cluster with 4 nodes set up. These nodes are 4 MSSQL servers.

What is the cluster core resources used for exactly?
Right now I see it offline but all of our SQL availability groups are syncing fine and not seeing any issues.
By this being offline how does it effect anything?

Also all of our servers are in the cloud if that matters.

2 answers

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Answer 1

TimCerling(ret) 1,156

Cluster core resources comprise a cluster IP, cluster network name (associated with cluster IP), and a quorum resource.

Your SQL instances have their own set of resources which include both a cluster IP and cluster network names which are separate from the cluster IP and network name. They operate independently, so the fact that the cluster IP and network name are offline should have no effect on the operation of the SQL instance.

Cluster resources being offline would affect management of the cluster, as those resources are needed for management of the cluster. However, if the cluster resources remain offline for an extended period of time, the cluster will stop working. Being offline can be a temporary condition, as the cluster will try to bring the resources back online.

Robert Ditusa 1 Reputation point

2020-08-09T14:00:29.873+00:00

So if the offline status stays offline for an extended period of time the sql instances will stop working? What would be an extended period of time?
You are saying after some time the SQL Availability groups will stop syncing then?
TimCerling(ret) 1,156 Reputation points

2020-08-10T14:02:44.273+00:00

According to https://learn.microsoft.com/en-us/previous-versions/windows/desktop/mscs/core-resources "If the core resources cannot be brought online, the cluster will not form and no resources in any group will be online". By that I would assume that you would be unable to fail your SQL resource group from one node to another. That in addition to the inability to manage the cluster.

Should be fairly easy to test in your environment.
Robert Ditusa 1 Reputation point

2020-08-10T14:37:56.33+00:00

Understand. My guess is there would be an issue with failover. I am working on updating the cluster the correct way. Currently we are using manual failover.
We are working on updating the application so automatic failover will work correctly.
Thank you.
Steve CLACK 0 Reputation points

2023-09-28T08:35:17.26+00:00

In my head (and this comes from trying to better understand the lack of core resources as clear as I possbly can for my own environments), the article quoted from https://learn.microsoft.com/en-us/previous-versions/windows/desktop/mscs/core-resources reads more like the cluster can not be initially built (Cluster will not form) if the core resources cannot initially be brought online.

I only question this because I've had a HyperV cluster and several SQL clusters with the Core Resource offline (due to a network issue) for months and the resources stayed online - I do believe we also had failover of resources without problems.
I'm trying to better understand if there has been a case where the Core Resource being unavailable has indeed eventually brought the cluster down.
I'm building a new cluster shortly and will try to failover (once the cluster has initially been formed) without cluster resource to see if i can break it.

Answer 2

Anonymous

Hi,
The cluster core resource is a set of resources required to be online in order to operate the cluster. Failure of a core resource does not necessarily lead to the failure of your cluster roles, e.g., the cluster name is offline and the cluster roles are still running.

You could open your Failover Cluster Manager and check which resource is offline.

For more details you could refer to this link
https://learn.microsoft.com/en-us/previous-versions/windows/desktop/mscs/core-resources

Best Regards,
Ian

Robert Ditusa 1 Reputation point

2020-08-10T12:35:49.66+00:00

I know which resources are offline. We have made a switch to cloud and the servers that are offline are not cloud.
All the cluster resources show offline. From my understanding since the SQL instance run on a different set a resources the cluster core resources does not to be online.

I will be adding the two new IP's from our cloud to the cluster core resources. Just trying to understand the impact when the cluster core resources are offline.
Anonymous

2020-08-20T02:22:52.47+00:00

Hi,
Just want to confirm the current situations. Please let us know if you would like further assistance.
If any reply is helpful, please "Accept Answer" to help other community members find it easier.

Best Regards,
Ian

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Failover Cluster core resource

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