You can run Windows Server 2012 in the same machine as the old version of Windows Server

The answer is “no.”. Because in Windows Server 2012, the biggest improvement in clustering is that it can be managed and deployed across servers. The new clustering feature is not backward compatible with older versions of Windows Server, so the cluster cannot be upgraded in a "scroll" manner, each node in the cluster needs to be logged out of the cluster, upgraded to Windows Server 2012 and then added to New server cluster for Windows Server 2012. Below are some of the new features of the Windows Server 2012 cluster. However, they are not supported in older versions of Windows Server: Storage Migration: Cluster-managed virtual machines can be migrated online to a new storage location, and virtual machines will always be available online during the migration process, similar to VMware VMotion. Cluster Shared Volume (CSV): This is not a new feature of Windows Server 2012. This feature was introduced in Windows Server 2008 R2 and re-modified and extended to be compatible with older versions of Windows. Multiple nodes in the same cluster can share the same file system, allowing one virtual machine hosted on any node in the cluster to be migrated to any other node. Cluster Aware Update (CAU): Servers in a Windows Server 2012 cluster can be updated with automatic scrolling. The cluster has been providing online services throughout the update process. Plugins that communicate with the API extend the behavior of CAU. There are many other new features in Windows Server 2012. However, if you want to use these features in a cluster, the entire cluster requires a unified upgrade to Windows Server 2012.