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JohnJY-4666 avatar image
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JohnJY-4666 asked JohnJY-4666 commented

best practice on Cluster network

Hi all,

We built windows 2016/2019 cluster with only one NIC
on two virtual VMs. Is this best practice?
should we have two NICs (one for data, one for private
heartbeat)?

Thank you!

windows-server-clustering
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LeonLaude avatar image
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LeonLaude answered JohnJY-4666 commented

Hi @JohnJY-4666,

I'm not sure if there are best practices for this, however there certainly are good practices.
From experience in the field it would be better with at least two (2) NICs, but this may depend entirely on the cluster, the purpose of the cluster and cost.

I would really recommend for you to go through John's very detailed post about Failover Clustering and networking basics/fundamentals in the post below:
https://techcommunity.microsoft.com/t5/failover-clustering/failover-clustering-networking-basics-and-fundamentals/ba-p/1706005

The above post should give you the essential information and some good practices.


If the reply was helpful please don't forget to upvote and/or accept as answer, thank you!


Best regards,
Leon

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Thank you so much for your insights. BTW, the two VMs mentioned are located in different site (one in production site and another at DR site). The cluster constantly lost heartbeats and failovered which impact SQL AG. In this situation at two different site, heartbeat NIC still recommended?

Thank you!

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The heartbeat communication is time sensitive, but it's a very lightweight packet, a single packet of 134 bytes so it does not require a lot of bandwidth.
If you have too much latency between your sites, you may want to consider leaving out the heartbeat.

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So from your saying, like in my situation, one NIC is fine, right? tried to get network team involved to see why caused heartbeats lost. the network team said no issue with switches .But, these are VMware VMs. The failover happened once per week. plus, SQL AG is configured to allow failback immediately which introduces more downtime.

another way I thought is to increase crossubnetthrehold from 10 to15. the failover cluster network threshholds have been fine turned with Windows 2016 OS.

Thank you for your help!

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@LeonLaude , thanks for your continuing support. still one more question to ask, in terms of heartbeats lost, the cluster failovered.
Does it mean that the cluster lost majority vote already in this case? (two nodes and one file share witness) Thank you!

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132010-fileshare.png



@LeonLaude, thank you for your continuing help. In the image, why the first scenario will be running (since it only has 2 votes)?

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fileshare.png (61.2 KiB)
LimitlessTechnology-2700 avatar image
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LimitlessTechnology-2700 answered JohnJY-4666 commented

Hello John,

As reference you can read this article: https://techcommunity.microsoft.com/t5/failover-clustering/no-such-thing-as-a-heartbeat-network/ba-p/388121

But all in all with one NIC you are ready to go with a Cluster service. Basically you can run the Cluster with 1 network, in the case that the NIC in one node fails, heartbeat will fail, this node will be removed from the membership and all roles moved to other available node. However, in case the virtual switch fails, it will fail for all members and the cluster will be down. The main recommendation is to create a separate network for heartbeat, as it is lightweight but important and you would like to avoid at all cost any heartbeat package lost that may bring down the cluster. However, if your network bandwidth is solid and the network usage is low for the cluster, one network is still an option.

Everything depends on the usage or purpose of the cluster itself.

Hope this helps with your query,
Best regards,

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HI LimitlessTechnology-2700,

the two VMs mentioned are located in different site (one in production site and another at DR site). The cluster constantly lost heartbeats and failovered which impact SQL AG. In this situation at two different site, heartbeat NIC still recommended?

Thank you very much!

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If it impacts production, go without heartbeat, it's main purpose is to monitor the cluster nodes' status to and maintaining the operation of the cluster.
As long as you monitor your cluster nodes any other way, you'll be fine.

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Hi LeonLaude,

Thanks for your continuing help.

Can I ask if windows core cluster fails, will SQL AG role fail? (AG and cluster group are on separate cluster group)technically, SQL AG role should not failover if windows cluster group fails, right?

Thank you!

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JohnJY-4666 answered LeonLaude edited

@LimitlessTechnology-2700

From the link https://techcommunity.microsoft.com/t5/failover-clustering/no-such-thing-as-a-heartbeat-network/ba-p/388121 and see the picture on stretch site, I did not see a dedicated heartbeat network created?

131579-strech-site.png


131664-strech-site.png



can you explain on this? Thank you!


strech-site.png (37.7 KiB)
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JohnJY-4666 avatar image
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JohnJY-4666 answered JohnJY-4666 commented

Hi all,

after reading https://techcommunity.microsoft.com/t5/failover-clustering/no-such-thing-as-a-heartbeat-network/ba-p/388121, it seems that there is no need to set up a dedicated network for heartbeats.

Can anyone help out whether my view of this article is right or not?

Thank you!

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Yes this is correct, there is no requirement for a dedicated/separate heartbeat network.

If the reply was helpful please don't forget to upvote and/or accept as answer, thank you!

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@LeonLaude So, if for the better practice, better to add one separate heartbeat network? I am getting lost now.

Thank you!

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In general (also as mentioned in the above link) if you're using heartbeat for your cluster, you would configure have a separate network adapter and a separate heartbeat network for your cluster, but as I already also mentioned, the heartbeat network adapter or heartbeat network is not required at all to run a cluster successfully.

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