Is it possible to share an NFS datastore between different ESX clusters (ESX 3.5 and 4)? I have come across a site that has the same mountpoint on different clusters - this sounds dangerous to me, but the only reference I could find on the VMware communities site on this said it is no problem. In the admin manual ESX and NetApp TR's I could not find a reference on this.
i think from the VM view, since your VM tools will be out of sync if they have DRS and all of that working. But I'm not sure if DRS works across datacenters or just across hosts within the same clusters. It does sound dangerous, but it is no different when you sharing it across one datacenter across different hosts. your just "spanning" on a different scale now.
I'm positive you will be fine in doing this. Its an NFS datastore and your storing files on the data store.
Each vmdk will get its on directory on the ifs mount and each ESX server will only care about that vmdk which is started with its resources.
So the fact that the two clusters are of different ESX version does not matter to the NFS share. The only thing I would caution would be to ensure the vmdka file compatibility between the two cluster if you ever needed to failover a sever to the higher or lower version cluster.
Bottom line is you should be more than ok sharing an NFS mount between two ESX clusters.
You cannot form ESX Host Cluster with different ESX versions (ESX 3.5 and 4).
You can have same mountpoint on different ESX Host, assume you have a virtual machine "A" running on ESX1 from NFS datastore nfsvol1, you can have the same nfsvol mounted on ESX2, but you cannot power on the virtual machine "A" on ESX2, ESX lock does not allow one to do this. Hence I dont see any harm with this.
NFs data stores are just like network file shares. Any OS can access shares. Likewise any version of ESX in any clusters can share same NFS data store. But like any share, two people(two hosts in this case) cant access the same file at same time. So as long as different hosts are accessing different files(VMs), you are good.