The basic architecture of the virtual machine has not changed in a long time. Because operating systems were built to operate physical devices, all VMs emulate broadly supported hardware, such as a specific NIC card or IDE disk controller. Hyper-V in Windows Server 2012 R2 supports the concept of a totally new architecture based on modern hardware with no emulated devices. This makes it possible to add a number of new features, such as secure boot for VMs and booting off of virtual SCSI or virtual network adapters. The catch is that guest support is limited to 64-bit versions of Windows 8 and Windows Server 2012
VM Direct Connect
Connecting to a running VM over RDP requires an active network connection, which you can’t always count on. In addition to an active network connection, the VM must have an IP address reachable by the system attempting to connect, a requirement with potential management and security issues depending on the environment in which you’re running. All this changes in Windows Server 2012 R2 and Hyper-V with the addition of VM Direct Connect. This feature allows a direct remote desktop connection to any running VM over what’s now called the VM bus. It’s also integrated into the Hyper-V management experience.
Extend replication to a third site
Hyper-V Replica in Windows Server 2012 is currently limited to a single replication target. This makes it difficult to support scenarios like a service provider wanting to act both as a target for a customer to replicate and a source to replicate to another offsite facility. Windows Server 2012 R2 and Hyper-V now provide a tertiary replication capability to support just such a scenario. By the same token, enterprises can now save one replica in-house and push a second replica off-site.
Replica frequency options
Hyper-V Replica in Windows Server 2012 provides a fixed replication interval of 5 minutes. This means you can’t replicate any faster, even if you have the hardware to support it. Nor can you replicate any slower, even if you don’t need such frequent copies. Two new options have been added in the Windows Server 2012 R2 release to support more frequent (30 seconds) and not so frequent (15 minutes) replication. This will even support an intermittent connection. By default, Hyper-V Replica will look for 12 missed cycles before it switches into a failed state. With the 15-minute cycle, you buy up to three hours of network downtime.
Compression for faster migration
Two new options in Windows Server 2012 Hyper-V help improve the performance of live migrations. The first is the ability to enable compression on the data to reduce the total number of bytes transmitted over the wire. The obvious caveat is that tapping CPU resources for data compression could potentially impact other operations, so you’ll need to take that into consideration. The second option, SMB Direct, requires network adapters that support RDMA. Microsoft’s advice: If you have 10Gb available, use RDMA (10x improvement); otherwise, use compression (2x improvement). Compression is the default choice and it works for the large majority of use cases.
Online VM exporting and cloning
One of the downsides of Hyper-V in Windows Server 2012 is the need to stop a running VM before you can export or clone it. In production environments, this is simply not an option. Windows Server 2012 R2 Hyper-V removes this restriction. It’s now possible to export or clone a running VM from System Center Virtual Machine Manager 2012 R2 with a few mouse clicks. As with pretty much anything related to managing Windows Server 2012, you can accomplish the same task using Windows PowerShell.
Online VHDX resizing
In Windows Server 2012 Hyper-V, it is not possible to resize a virtual hard disk attached to a running VM. Windows Server 2012 R2 removes this restriction, making it possible to not only expand but even reduce the size of the virtual disk (VHDX format only) without stopping the running VM. What you can’t do with this feature: Compress an online VHD. You can make these adjustments from System Center Virtual Machine Manager 2012 R2, Hyper-V Manager, or the command line using PowerShell. You can use PowerShell to set the disk size to the current disk consumption if you want to reduce it to the absolute minimum.
Windows Server 2012 R2 includes the ability to limit individual VMs to a specific level of I/O throughput. In the screenshot at left, you can see the two settings for minimum and maximum IOPS. In the initial release of Windows Server 2012 R2, the only number that really makes a difference is the maximum limit. The IOPS are measured by monitoring the actual disk rate to and from the attached virtual hard drives. If you have applications capable of consuming large amounts of I/O, you’ll want to consider this setting to ensure that a single I/O-hungry VM won’t starve neighbor VMs or take down the entire host.
Dynamic Memory support for Linux
Microsoft continues to improve support for Linux VMs. In the Windows Server 2012 R2 release, Hyper-V gains the ability to dynamically expand the amount of memory available to a running VM. This capability is especially handy for any Linux workload (notably Web servers) where the amount of memory needed by the VM changes over time. In environments with many Linux VMs, dynamic memory becomes even more critical to efficiently manage the total memory used by all running VMs. Windows Server 2012 R2 Hyper-V also brings Windows Server backups to Linux guests.
With Windows Server R2 Hyper-V, Windows guest clusters (think traditional Windows Server failover clustering but using a pair of VMs) no longer require an iSCSI or Fibre Channel SAN, but can be configured using commodity storage: namely a shared VHDX file stored on a Cluster Shared Volume. Note that while the clustered VMs can be live migrated as per usual, a live storage migration of the VHDX file requires one of the cluster nodes to be taken offline.
Work Folders bring the functionality of Dropbox to corporate servers. Install this role on a Windows Server 2012 R2 system, and you get a fully functional, secure file replication service. The initial release will support only Windows 8.1 clients. Support for Windows 7 and iPad devices is promised for the future, with Android clients further down the list. Like Dropbox, Work Folders will keep copies of files on both the server and the client, performing sync operations whenever the client establishes a connection with the server.
Desired State Configuration
Maintaining configuration on lots of servers has been a thorn in the side of system administrators for as long as anyone has been running lots of servers. Many point solutions and countless custom in-house tools have been devised to accomplish the task. Now there is a feature built into Windows Server 2012 R2 that makes it possible to programmatically establish a baseline of roles and features, then monitor and update any system that doesn’t match the desired state. Desired State Configuration requires PowerShell 4.0, which provides a number of new cmdlets to accomplish both the monitoring and the administration of specific states
This might be the single most exciting new feature in Windows Server 2012 R2. In essence, Storage Tiering is the ability to dynamically move chunks of stored data between different classes of storage, such as fast SSDs and slower hard drives. Many high-end storage systems have had automated tiering for years, but this is the first time you are able to do it at the operating system level. Microsoft uses a heat-map algorithm to determine which chunks of data are seeing the most activity and automatically moves the “hottest” chunks to the fastest tier. You can adjust the settings for how and when the data is moved using PowerShell
Closely related to Storage Tiering is the ability to pin selected files to a specific tier. Pinning makes it possible to ensure that files you always want on the
fastest storage, such as boot disks in a Virtual Desktop Infrastructure deployment, will never be moved to the slower storage tier. Otherwise, files that you always want to take advantage of SSDs might be moved to the HDD tier after some period of relative inactivity.
Write Back Cache
When you create a new storage volume in Windows Server 2012 R2, you also have the option to enable something called the Write Back Cache. This feature sets aside an amount of physical storage, typically on a fast SSD, to use as a write cache to help smooth out the ups and downs of I/O during write-intensive operations. This can be seen in a typical database scenario where a large volume of disk writes may exceed the ability of the drive controller and disks to keep up. The cache would eliminate any pauses caused by an overwhelmed storage subsystem.
Deduplication on running VMs
Data deduplication in Windows Server 2012 is a nice feature, but one thing it cannot do is deduplicate running virtual machines. That limitation is removed in Windows Server 2012 R2, albeit specifically for VDI (Virtual Desktop Infrastructure) deployments on SMB 3.0. That said, this new capability could greatly increase the overall effectiveness of deduplication for VDI implementations. As a side benefit, deduplication greatly improves boot performance of virtual desktops. In addition to storing the VMs on SMB 3.0 (required), Microsoft highly recommends using Scale-Out File Server on Windows Server 2012 or Windows Server 2012 R2. Cluster Shared Volumes are supported for high availability.
If you’ve ever had a disk fail in a RAID array, you know a disk rebuild can take many hours. And with more and more deployments of really large physical disks, the amount of time required to rebuild a drive will only get longer. Microsoft addressed the issue of lengthy CHKDSK checks in Windows Server 2012, which greatly reduced the time required to scan and repair a single disk. Windows Server 2012 R2 adds the ability to perform a parallel rebuild of a failed Storage Spaces drive, reducing the amount of time required by an order of magnitude. Demonstrations at TechEd showed a rebuild of a 3TB disk taking less than an hour.
Windows Server 2012 R2 addresses the need to incorporate personal devices like iPads into the enterprise environment. At the simplest level is a new Web Application Proxy that allows you to provide secure access to internal corporate websites, including SharePoint sites, to any authorized user. One step further is a new capability called Workplace Join, which allows users to register personal devices with Active Directory and gain certificate-based authentication and single sign-on to enterprise applications and data. Standard tools like Group Policy apply here for controlling conditional access on either an individual or group basis.
Multitenant VPN gateway
Microsoft has added a number of new features to make it easier to provide secure communications between on- and off-premise networks. The new multitenant VPN gateway lets you implement site-to-site connectivity to multiple external sites via a single VPN link. This feature is aimed at both hosting providers and large organizations looking to implement connectivity with multiple sites or external organizations. Each site-to-site network connection require a separate gateway in Windows Server 2012, adversely impacting both cost and ease of implementation when more than a few connections are required for a single application. Windows Server 2012 R2 does away with this limitation
Windows Server Essentials role
While this might not sound like a big deal, it has the potential to make life much easier for any organization with a geographically distributed network. With Windows Server 2012, you have to use a completely different installation source for Windows Server Essentials. For large organizations, this can impact both distribution strategy and configuration management. The Windows Server Essentials role in Windows Server 2012 R2 brings with it a number of other features — including BranchCache, DFS Namespaces, and Remote Server Administration Tools — that are typically implemented in remote office settings