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JohnJY-4666 avatar image
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JohnJY-4666 asked Yufeishao-msft commented

Is this bad design on stretch cluster?

Hi all,

one of my clients has all stretch clusters with SQL availability group role set up with
two VMware nodes(one at production site and one at DR site(FSW at DR site)(windows 2012R2 up)
Node1(1NIC ) ----- Node2 (1NIC)+FSW (storage appliance)
Production site ---- DR site

Is this a bad design?

Thank you!

sql-server-generalwindows-server-clustering
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Since you ask about design, it is better to give a question a title that helps people decide if they can help. The title Is this bad design? does not do that.

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LimitlessTechnology-2700 avatar image
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LimitlessTechnology-2700 answered

Hello @JohnJY-4666

I don't see any reason why it wouldn't work, but personally I would not have the FSW as part of the storate of one of the nodes. Ideally nowadays would be easy to create a cloud drive to provide resilience to the equation.

Please check:

https://docs.microsoft.com/en-us/windows-server/failover-clustering/file-share-witness

Best regards,

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JohnJY-4666 avatar image
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JohnJY-4666 answered

Hi all,

is there an issue with cluster network which has only one route?

Thank you for your insights.

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Yufeishao-msft avatar image
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Yufeishao-msft answered Yufeishao-msft commented

Hi @JohnJY-4666


for multi-site stretched-cluster, if you do not have a third site, then cloud witness is the optimal solution, more simple solution is that put up a FSW on another server in one of the data centers and make sure it is running on separate circuit.
A witness share needs to be available for single connection, the purpose of the FSW is to have something else that can count as a vote in situations where the number of configured nodes isn’t quite enough for determining quorum.

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If the answer is the right solution, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".

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JohnJY-4666 avatar image
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JohnJY-4666 answered Yufeishao-msft commented

Hi @Yufeishao-msft

Thank you for the insights. Due to two different sites which are likely to have transient network issues, what would happen if heartbeats get lost between these two nodes (one at PR and another at DR)?

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A "disaster" is not the Internet going down for a few mins. This is not what a DR site is for or intended to accomplish.

A "disaster" is your data center burns to the ground and is unrecoverable.

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Heartbeat may be lost due to network congestion or no response within the ping time you set.
For example, SameSubnetThreshold=20 and SameSubnetDelay=2 which means The heartbeat will NOT give up unless 20 pinges each send after 2 sec fail to get any response from the servers. Which mean the heartbeat would wait 40 seconds before initiating failover.

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JohnJY-4666 answered Yufeishao-msft commented

@TomPhillips-1744 no need for separate heartbeat network?

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A dedicated heartbeat network between cluster nodes can make the cluster more stable.
If your NIC which hosts both cluster and client communication gets saturated more often I would suggest you set up heartbeat. It does not add complexity.

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@Yufeishao-msft Thank you. Is it still required as before which no gateway IP should be specified for heartbeat NIC?
If yes, is it possible to set up a dedicated network between two sites which does not need gateway on a heartbeat NIC?

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In general it is recommended to use static IP addresses for servers, whether it's Heartbeat or not.
It is important for have ​a dedicated network for internal cluster (also known as heartbeat or private) communication

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JohnJY-4666 answered

Hi All, can anyone share whether you add a separate network dedicated to intra cluster communication in multi-subnet stretch cluster? thank you!

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