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
Online virtual disk resizing
VHDX files attached to a SCSI controller can be increased or decreased while the VM is running. You can use either the Edit Virtual Hard Disk Wizard, which is a part of Hyper-V Manager, or the Resize-VirtualDisk cmdlet in PowerShell. Online disk resizing works well with Generation 2 VMs as they use a SCSI disk by default. To perform an online resize with Generation 1 VMs, you will need to add a new SCSI controller. By default, Generation 1 VMs use an IDE controller.
Hyper-V R2 adds the ability to configure a minimum and a maximum IOPS allocated to individual VMs. The minimum value is not fully functional in the preview release, but is seen as a way to guarantee a minimum level of IO to a VM. The importance of this feature comes to light when you have multiple I/O-hungry VMs running on the same host. Storage QoS is also tied specifically to VHDs attached to a SCSI controller.
Remote Desktop enhancements
Previous versions of Hyper-V required a working and connected network to attach to a running VM from any machine other than the server. This is not a requirement with Hyper-V R2, which now supports a direct RDP connection to any running VM via the "VM bus." This means you can connect to a remote VM before assigning an IP address. In addition, a new Enhanced Session Mode supports access to audio, clipboard, display configuration, drives, smart cards, supported plug-and-play devices, and USB devices on the remote system. This functionality is currently limited to Windows 8.1 Preview and Windows Server 2012 R2 Preview guests.
SCVMM 2012 R2
It's easy to feel overwhelmed if you've never worked with Microsoft's System Center before. Many options exist, some of which must be accomplished either prior to or in conjunction with others. You will need to learn the new cloud terminology and understand the concepts of fabric and tenants, among others. If you're serious about evaluating SCVMM 2012 R2, you'll need a hefty lab for setup, according to Microsoft's evaluation plan. Microsoft recommends a total of six physical servers, each with 24 CPU cores and 128GB of memory. You'll also need a minimum of two physical switches to separate the networks.
One of the key themes Microsoft has promoted with all of the R2 releases is cloud integration. You can see this focus in multiple areas, including networking, service templates, and even Windows PowerShell. We'll address these topics from the perspective of administrators and IT management.
Large enterprises and service providers chafed at a significant limitation in Windows Server 2012 Hyper-V related to multiple tenants on a single host. This limitation required a single hardware NIC for each unique hosted gateway. That puts a big cramp on server hardware capable of running large numbers of VMs. In Windows Server 2012 R2 Hyper-V, this limitation goes away with support for multitenant virtual gateways.
SCVMM 2012 R2 is now capable of managing the entire data center networking infrastructure to include multiple sites connected using a site-to-site VPN. This role makes sense for SCVMM when you consider the potential for gotchas like IP address conflicts and multiple domains. Integration with IPAM (IP Address Manager) adds another implement to the toolbox for dealing with multiple IP address spaces.
System Center Virtual Machine Manager 2012 R2 recognizes the new Generation 2 VMs, but won't let you migrate one to a Windows Server 2012 or earlier host.