HashiCorp vault cluster nodes across two DCs with open source

I have two questions.
Can we deploy vault nodes in even numbers? if yes, what would be the resultant quorum count?
If we deploy 6 nodes and spread across two datacenters (3 for each DC), what will happen if there is a connectivity issue between DCs? would it cause a split brain scenario like the DC which has no leader node will have new a leader?

You have not specified which storage backend you are referring to.

I will assume you mean Integrated Storage (Raft), since this is the only case where Vault nodes actually participate in a quorum.

Quorum is always a simple majority. So with 2 or 3 nodes the quorum is 2. 4 or 5 nodes, the quorum is 3. 6 or 7 nodes, the quorum is 4.

The current leader will observe it is no longer able to contact a quorum (4 nodes), so the Vault service will go offline in both DCs.

Thanks you very much for responding.
This means, nodes in a single cluster cannot be spread across two DCs and achieve DC high availability no matter what the count of nodes is. am I right?

Deploy 7 nodes in a cluster.
4 nodes in 1st DC and 3 nodes in 2nd DC
If first DC is unavailable, then cluster becomes unavailable.
There is no way to tackle it with OSS.
With enterprise, we could deploy a DR cluster in 2nd DC.

OSS isn’t designed for DR just HA.

As you say you’d need the Enterprise version for DR.