First look: Windows Server 2012 R2 Hyper-V shines on
Preview editions of Hyper-V 2012 R2 and System Center Virtual Machine Manager 2012 R2 pick up where the strong initial releases left off
Network virtualization was initially introduced with the release of Windows Server 2012. Logical networks are the foundation upon which all other network virtualization pieces are laid. When you first get started with SCVMM, you must configure a logical network to which all other virtual networks can connect. By default, SCVMM will create a new logical network where all devices are interconnected and visible. SCVMM 2012 R2 supports the creation of VLAN-based independent networks as well as Private VLAN (PVLAN) networks.
On top of this is the new NVGRE (Network Virtualization using Generic Routing Encapsulation) gateway for site-to-site connectivity. NVGRE is a relatively new standard (currently in draft status) specifically designed for cloud computing environments. The basic principle is using encapsulation of Layer 2 packets for transmission over Layer 3 networks. Layer 2 is typically where all signaling and interaction with the physical layer (think MAC addresses) takes place. NVGRE makes it possible for devices on two completely separate Layer 3 networks (think IP addresses) to interact as if they were on the same Layer 2 subnet.
SCVMM adopted the concept of service templates quite some time ago, but in SCVMM 2012 R2, they really start to make sense. When you need to consistently create the same kind of service, be it a network gateway or provisioned storage resource, you'll want to use a service template. Microsoft announced at TechEd 2013 in New Orleans that it intends to make System Center components available as service templates in the future. Company reps also demoed the use of new script options to automate the creation of guest clusters with VMM Service Templates. On the networking side, you'll be able to use service templates to automate the provisioning of edge gateways and the full range of networking services.
Microsoft has traditionally offered token support for running various Linux distributions on Hyper-V, but that has started to change. Windows Azure got the ball rolling by offering a wide range of Linux-based applications, and the ball has bounced on over to System Center. SCVMM 2012 R2 now supports the creation and deployment of CentOS, Red Hat, Suse, and Ubuntu virtual machines, which in turn can be monitored via System Center Operations Manager. Some of these distributions, including Red Hat Enterprise Linux 5.9 and Ubuntu Server 12.04 LTS, have Microsoft's Linux Integration Services for Hyper-V already installed.
What doesn't work yet
SCVMM 2012 R2 does not support the management of Storage Spaces for Scale-Out File Servers on Windows Server 2012, leaving your options at Server Manager or PowerShell. The Physical to Virtual (P2V) functionality is being retired with SCVMM 2012 R2, so you'll have to find some other way to convert existing physical machines into virtual ones if that's a requirement. You can't manage the new storage tiering or write-back cache features of Windows Server 2012 R2 directly with VMM. You can still do that with PowerShell, and in theory, you could automate scripts through VMM to accomplish the task if necessary.
When adding a new host, System Center Virtual Machine Manager 2012 R2 will check for hardware support of features such as Multipath I/O and let you know if they're not enabled.