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  • 1.  vSAN metro clusters are not supported with FT.

    Posted Dec 21, 2022 08:14 AM

    In documentation for FT (https://docs.vmware.com/en/VMware-vSphere/8.0/vsphere-availability/GUID-2A87B967-5BBB-4394-B1E6-EE87D50A2A86.html), it is stated: "vSAN metro clusters are not supported with FT.". My understanding is then, that a vSAN (2-node) Stretched Cluster will not support FT.

    My question is actually regarding the use case for a vSAN (2-node) Stretched Cluster, if the the 2 vSAN nodes, while being in separate datacenter buildings, have the vmkernel connection for vSAN made by a directly connected 25 Gb fiber (latency around 0,1 msec.). This setup use of cause the supported Witness separation, i.e. the Witness and other vmkernels use the slower switched network. 

    The question is then, if such architecture could be configured as a 2-node cluster (instead of a Stretched Cluster)? I guess the recommendation to use a Metro/Stretched Cluster when having 2 separate buildings is with the assumption, that using a network with several switches will introduce increased latency and so the need for a Stretched Cluster configuration with better tolerance for latency.

    The motivation for my question is, to understand where the vSAN/FT limitations actually are, so in the end to understand if an architecture with 2 vSAN nodes in separate building (+additional wittness server), but with a separate direct 25 Gb vSAN vmkernel connection and an additional separate direct 25 Gb FT vmkernel will be supported and functional for both vSAN and FT?  

    Best regards


  • 2.  RE: vSAN metro clusters are not supported with FT.
    Best Answer

    Posted Dec 21, 2022 08:44 AM


    it is not supported, not on two-node either when those two nodes are in two different physical locations. It is a testing limitation, and a limitation in terms of bandwidth and latency. (Yes I know you don't have that problem, but in general).

    The issue is being worked on by the engineering team though. In your case you could try to get an "RPQ", which is basically one-off support for this scenario. You will have to work with a local VMware representative on this though.

  • 3.  RE: vSAN metro clusters are not supported with FT.

    Posted Jan 25, 2023 12:25 PM

    Thanks depping for the answer.
    As I understand it, a "2-node direct connect", if the direct connection are end-2-end fiber connections between the 2 nodes and without any delaying switches, would practically don't matter, if nodes was in same room or in separate buildings, but that this has not been tested. Could be tested by "RPQ", but if that would be with our new equipment, we would have to decide on a setup based on a qualified guess in the first place.

    Best regards