Microsoft introduced several new features in Windows Server 2012 and Windows Server 2012 R2 Hyper-V, making the number of additions to Windows Server 2016 Hyper-V seem modest. Still, there are a number of noteworthy Hyper-V features in the latest version, including shielded VMs, improved storage resiliency, changes to PowerShell, and production checkpoints. Here's a rundown of what Hyper-V features to expect.
Checkpoints, which were previously referred to as snapshots, have existed in Hyper-V since its inception. They allow administrators to roll back a virtual machine (VM) to an earlier point in time without having to restore a backup. The problem with using checkpoints is that they didn't work very well with application servers. If used improperly, a Hyper-V checkpoint can corrupt databases and can severely damage applications.
Production checkpoints function in much the same way, except they use the power of the Volume Shadow Copy Services. When you create or apply a checkpoint, the process works similar to creating or restoring a backup, allowing admins to avoid various corruption issues often associated with the use of checkpoints. Production checkpoints will be enabled by default in Windows Server 2016 Hyper-V; however, it will also be possible to revert to the old checkpoint model if necessary.
The basic idea behind shielded VMs is that a fabric can now be designated as the owner of a VM. Therefore, the VM cannot be moved to another fabric nor will it function in another. Shielded VMs are encrypted to prevent unauthorized access to VM contents. This encryption can be achieved through the use of BitLocker. The new version of Hyper-V will support virtual TPM, which allows a VM to be BitLocker-encrypted.
In previous versions of Hyper-V, the momentary loss of storage connectivity could cause a VM to fail. Even though admins could use failover clustering to fail a VM over to another cluster node, that still requires storage connectivity. And sometimes a failover is overkill.
For example, in a Hyper-V deployment in which a number of cluster nodes are connected to an iSCSI target, the iSCSI target will suffer from low bandwidth and intermittent connection failures will become common during periods of peak activity. A crash would occur every time a VM lost connectivity for more than a minute.
The storage resiliency feature is designed to detect momentary loss of connectivity to VM storage and pause the VM until storage connectivity is re-established. But performing a cluster-level failover is still an option.
PowerShell can run scripts or cmdlets on remote Windows Servers in several ways. The best-known method involves using the Invoke-Command cmdlet. An administrator would enter the Invoke-Command cmdlet, followed by the –ComputerName parameter, the credentials for the remote machine, and the command that they wanted to run.
With previous versions of Hyper-V, it was possible to use the Invoke-Command cmdlet to run a command on a Hyper-V VM. To do so, however, the target VM needed network connectivity.
In Windows Server 2012 R2, admins have the ability to copy files into a VM -- even if no network connectivity exists. The file copy process could make use of the VMBus in the absence of network connectivity. In Windows Server 2016, the PowerShell Direct feature builds on this concept.
Windows Server 2016 will allow administrators to remotely run PowerShell cmdlets or scripts on a VM, even if the VM is not connected to the network. The process uses the power of the VMBus and the Invoke-Command cmdlet. This means replacing the cmdlet's ComputerName parameter with the VMName parameter.
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