How to configure cluster traffic priority on a windows server

During writing my current cluster network series, I saw some points some people normally miss when configuring a Microsoft Cluster via Failover Cluster Manager.

One thing is, that they do not prioties Cluster Networks against each other and to change the routing interface.

The following task must be done on every cluster server. We change the connection settings so that our routed traffic goes over the management interface first.

1. navigate to your network adapter properties and open the advanced settings in the menu bar.

06-07-_2015_15-27-332. in the next menu you move you management interface which will be your gateway on the highest place.

Network

 

So thats all for the routing part. For the next point you connect to a cluster node. You only need to do that operation once per cluster.

1. Check your Cluster Network. All Networks should be up and running.

Clusternetwork

2. Now you need to open and change the network metric. Here the lowest metric means, that cluster network has the highes priority. I recommand you to give cluster heartbeat traffic the highest priority because if that traffic fails, your node will go down within the cluster.

I set that configuration on a scale out fileserver, so my traffic will be priotiesed as followed:

high -> Cluster – Storage 01 – Storage 02 – Management -> low

So that means I need to run following script:

You can check the result with:

The result should look like the screen below.

metric

Thats all, only small changes but improves the stability of your clusters in a high rate.

 

 

How a Microsoft Failover Cluster works

During my daily work in the field I often have to explain how a Failover cluster in the Microsoft world is working. Currently I mostly discribe three kinds of clusters. First is the Clustertyp which is used for DHCP Failover Cluster, like discribed in a former blogpost. The other is a DAG or Database availability group, how it is used in Exchange and Failover Cluster how it works in Scale out Fileserver and Hyper-V Cluster.

Today I want to focus on the Fileserver and Hyper-V Failover Cluster and try to explain it.

At first, you need to know such a failover cluster must have an uneven number of cluster members.

Why do we need an uneven number of cluster member? The reason for is a thing named split brain.

Source wikipedia:

Split-brain is a term in computer jargon, based on an analogy with the medical Split-brain syndrome. It indicates data or availability inconsistencies originating from the maintenance of two separate data sets with overlap in scope, either because of servers in a network design, or a failure condition based on servers not communicating and synchronizing their data to each other. This last case is also commonly referred to as a network partition.

An uneven number of cluster members? But dies this mean I can only have 1,3,5, … etc. servers in my cluster?

Normally yes but hear comes the Magic. The uneven  member do not need to be a Server, it could also be a share or LUN. This share is named Cluster Shared Volume (CSV) or cluster witness. Every Server and the cluster witness have the same wight in the cluster.

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Now one server catches the witness and becomes the “clustermaster” and has more votes in the cluster. He will give the direction for the other nodes.

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What happens if one cluster when the cluster master files? Very easy, together with the cluster master, the cluster shared volume fails too. That means at the end we will have an uneven number of cluster nodes and there won’t be a split brain.

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If a cluster member failes, the witness will be disconnected and deaktivated. That will also bring an uneven number of cluster nodes and we won’t run in split brain.

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Now you will ask, I have more than two nodes. What will happen if the connection splits the cluster in two halfes? which means it would force the split brain issue again!

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The cluster member will notice their numbers on both sides. Than the cluster will go and run on the uneven cluster half.

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Cool new Showcast from @WorkinghardinIT & @Hypervserver

A new showcast with my two most inspiring friends and idols. The Hyper-V Amigos Carsten Rachfahl and Didier van Hoye.

 

OpenManage Server Administrator Management Interfaces on Windows OS

The Dell TechCenter global published a manuel, which discribes how to install Open Management Server Administrator on a Windows Server OS.

You can download it here.