TryllZ
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Witness with 3 node setup ?

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Hi,

I have been looking through design considerations for vSAN, I am not able to find a configuration that shows how to go about 3 ESXi hosts in a vSAN and a Witness.

For a 3-node design it shows 2 hosts plus a witness, no where have I been able to find a configuration with 3 ESXi hosts and a Witness, and the fact that vSAN requires 3 hosts in a cluster is confusing, am I misunderstanding something.

Could some one explain a scenario with 3 ESXi hosts, and a witness.

Thank You

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TheBobkin
VMware Employee
VMware Employee

Hello TryllZ​,

"I have been looking through design considerations for vSAN, I am not able to find a configuration that shows how to go about 3 ESXi hosts in a vSAN and a Witness."

That's because that is not a recommended configuration.

"For a 3-node design it shows 2 hosts plus a witness, no where have I been able to find a configuration with 3 ESXi hosts and a Witness, and the fact that vSAN requires 3 hosts in a cluster is confusing, am I misunderstanding something."

So, the two 3-node configurations that would require a Witness are as follows:

1+1+1 Stretched cluster - one data-node at each site and Witness at 3rd site to store the witness components and determine quorum in the event of failure of one site or network communication loss between the data-sites.

2+1 DirectConnect - basically two data-nodes connected without a switch and Witness stored elsewhere for witness component placement and determining quorum in the event of a node/Disk-Group/controller/hardware failure on one data-node.

"Could some one explain a scenario with 3 ESXi hosts, and a witness."

If you want to configure a 3-node cluster then you have three recommended options, either as a either of the above or just as standard 3-node cluster with 3 data-nodes and no witness.

The only use-case that a lop-sided 3-nodes + Witness cluster would make sense is a 2+1+1 cluster with some disposable FTT=0 VMs pinned to the site with 2 data-nodes.

Bob

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TheBobkin
VMware Employee
VMware Employee

Hello TryllZ​,

"I have been looking through design considerations for vSAN, I am not able to find a configuration that shows how to go about 3 ESXi hosts in a vSAN and a Witness."

That's because that is not a recommended configuration.

"For a 3-node design it shows 2 hosts plus a witness, no where have I been able to find a configuration with 3 ESXi hosts and a Witness, and the fact that vSAN requires 3 hosts in a cluster is confusing, am I misunderstanding something."

So, the two 3-node configurations that would require a Witness are as follows:

1+1+1 Stretched cluster - one data-node at each site and Witness at 3rd site to store the witness components and determine quorum in the event of failure of one site or network communication loss between the data-sites.

2+1 DirectConnect - basically two data-nodes connected without a switch and Witness stored elsewhere for witness component placement and determining quorum in the event of a node/Disk-Group/controller/hardware failure on one data-node.

"Could some one explain a scenario with 3 ESXi hosts, and a witness."

If you want to configure a 3-node cluster then you have three recommended options, either as a either of the above or just as standard 3-node cluster with 3 data-nodes and no witness.

The only use-case that a lop-sided 3-nodes + Witness cluster would make sense is a 2+1+1 cluster with some disposable FTT=0 VMs pinned to the site with 2 data-nodes.

Bob

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TryllZ
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HI,

Thanks for the reply.

Could you just let me know if my configuration is a stretched cluster, I'm thinking if latency will come into the picture.

Where I have a vCenter at data centre which is physically distant from the site, and the site has 3 hosts which will have vSAN.

Because where I have read stretched-cluster it says host nodes are in 2 physically distant sites, Site A, and Site B, and witness is at a 3rd site. This is different from my scenario where I have 2 sites, 1 with vSAN on 3 hosts, and the other with vCenter server.

Thank You

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TheBobkin
VMware Employee
VMware Employee

Hello TryllZ

"Where I have a vCenter at data centre which is physically distant from the site, and the site has 3 hosts which will have vSAN."

Where the vCenter managing the cluster resides doesn't matter with regard to stretched/non-stretched - if all the vSAN nodes reside in one location then a non-stretched cluster configuration is what you want (with no Witness of course as you have 3 nodes).

Bob

TryllZ
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Appreciate the clarification.

I believe no latency will occur, as I understand.

Thank You

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