Can 2-node or Stretched be used as client or server cluster with vSAN HCI Mesh?

I had this question today, probably sparked by my post earlier where a showed a single-node cluster being able to leverage HCI Mesh to mount a remote vSAN Datastore. The question was if this also works with 2-node vSAN or with a vSAN Stretched Cluster. Unfortunately, the answer is no, a 2-node cluster or a vSAN Stretched Cluster is not supported with HCI Mesh today. Yes, this is a hard limit today, meaning that the “health check”, which is done before mounting the datastore, will actually report the issue and not allow it to progress. You can imagine that this is the result of the latency and bandwidth/throughput requirements there are in place for vSAN HCI Mesh today. This may, or may not, change over time.

On the community forums, a question was asked around the use of site locality in a vSAN Stretched Cluster. When you create a stretched cluster in vSAN you can define within a policy how the data needs to be protected. Do you want to replicate across datacenters? Do you want to protect the “site local data” with RAID-1 or RAID-5/6? All of these options are available within the UI.

What if you decide to not stretch your object across locations, is it mandatory to specify which datacenter the object should reside in?

The answer is simple: no it is not. The real question, of course is, would be: should you define the location? Most definitely! If you wonder how to do this, simplicy specify it within the policy you define for these objects as follows:

The above screenshot is taken from the H5 client, if you are still using the Web Client it probably looks slightly different (Thanks Seamus for the screenshot):

Why would you do this? Well, that is easy to explain. When the objects of a VM get provisioned the decision will be made per object where to place it. If you have multiple disks, and you haven’t specified the location, you could find yourself in the situation where disks of a single non-stretched VM are located in different datacenters. This is, first of all, terrible for performance, but maybe more importantly also would impact availability when anything happens to the network between the datacenters. So when you use site locality for non-stretched VMs, make sure to also configure the location so that your VM and objects will align as demonstrated in the below diagram.

vmware vsan