vSAN Small business design confusion.

Hi,

I'm setting up a small business with 2 serverrooms and one rack per serveroom. The rooms are close together and theres 10G fibre between them.

I would like to have two nodes in each serverroom for a total of 4 ESXi hosts.

We are looking at All-flash vSAN with dedub and compression. Around 8TB of data (before dedub and comp.) and around 40VMs.

VM's in room A should have the copy in room B and vice versa.

Problem is I need Fault domain to control this, but as far as I can tell from the documentation, the requirement is 3 rooms (fault domains) as a minimum?

Hope someone can help point me in the right direction with this setup.

Thanks in advance.

/Martin