YOU CAN, BUT YOU MAY NOT!!
This might be the weirdest way to begin a blog post but I wanted to put this word out, loud and clear! Since the release of vRealize Operations 6.0, we all know that vROps can be deployed in a cluster architecture with multiple nodes which bring in resiliency and scalability to the solutions by just adding a node to an existing cluster. I have discussed this architecture and the benefits of the same in an article before.
In that article I have also highlighted that you should deploy vRealize Operations Manager Cluster within the same site as that is the requirement for deploying the solution. Since then, their have been a number of occasions when I have been asked this question as people want to use the cluster architecture to their advantage and deploy the solution across sites to ensure that the cluster is alive even if one of the sites completely fails.
This across site cluster deployment will not work if it is more than a 2 NODE cluster, because vROps nodes randomly distribute data to the nodes in the cluster while storing a copy of the same in some other node, there is no way that those nodes will always be in different sites always (you cannot control that). Hence imagine you have a 4 node cluster and the N1 and N2 are in Site A while N3 and N4 are in Site B. A metric collected by N1 can be replicated as a copy on N2, N3 or N4 and you do not have any control over it, hence if a metric is copied to N2 and the Site A fails, then you will lose that data, hence this solution cannot be a across site solution.