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FAQ: Three questions on Hyper-V 3.0 features in Windows Server 2012

Administrators can improve VM automation, storage performance and data protection by using the new Hyper-V 3.0 features in Windows Server 2012.

Few technologies have affected the data center like server virtualization. Hypervisors form the core of any virtual server -- converting the system's physical computing resources into virtual ones and then managing those resources allocated to each virtual machine. But as computing, networking and storage hardware evolves, hypervisors must also keep pace in order to leverage new hardware and standards. The release of Microsoft Windows...

Server 2012 has brought some changes to Hyper-V 3.0 features. Let's address some questions about several important advances.

How do the virtual disk files in Hyper-V 3.0 compare to earlier versions of Hyper-V?

Virtual machines run in the server's memory, but Hyper-V VMs are stored and protected in enterprise storage subsystems on LUNs using the virtual hard disk (VHD) format. Previous versions of Hyper-V such as the one under Windows Server 2008 R2 imposed a VHD size limit of 2 TB for any dynamic or differencing VHD volume. Hyper-V 3.0 includes an updated VHDX format that increases this limit to 64 TB and allows the storage of enormous VMs like database or email systems. It is unlikely that most enterprises would need such huge VM volumes anytime in the near future, so this update should support the continued growth of virtual machines well into the future.

The Replica feature can be used to copy production VMs over to test and development systems. That way, replicated data can be used without jeopardizing production data.

The threat of VM data loss or corruption is another critical concern for IT administrators, so the VHDX format also logs any changes to a VHDX volume in metadata. If a problem occurs with the volume, the disk can be restored to a prior state more easily than a traditional recovery process.

And the VHDX format makes important changes to the way Hyper-V 3.0 uses VHDX disk space. For example, as hard disks get larger, disk cluster sizes can also grow, allowing for inefficient performance and use of physical storage space. VHDX can manage virtual clusters at a svelte 4 KB for better storage performance and space utilization.

Do Hyper-V 3.0 features offer better automation capabilities than previous versions? Should automation features be enough to warrant a move to Hyper-V 3.0?

Automation has emerged as an important consideration as virtualized environments grow, and the relationship between physical systems and virtualized workloads is becoming more abstract. Hyper-V 3.0 introduces more than 140 Hyper-V cmdlets for Windows PowerShell scripting that IT administrators can use to manage VMs and VHDX files without needing expertise in Windows Management Instrumentation (WMI) interfaces.

Scripting with these new cmdlets will require Windows Server 2012 with the Hyper-V role installed and a server that supports virtualization. Administrators will also need access to the Administrator or Hyper-V Administrator groups.

As examples, consider that new cmdlets allow administrators to create new virtual machines with specific names, retrieve lists of all VMs, create new VHDX files of designated names, start individual VMs or groups of VMs and connect VMs to desired virtual network adapters or switches. Administrators can also import, export, migrate and monitor VMs and VHDX files.

The complete list of Hyper-V 3.0 cmdlets can be found in the Windows Server 2012 documentation, but you can start to appreciate the flexibility available for PowerShell scripting.

Are there any better ways to protect my virtual machines using Hyper-V 3.0 under Windows Server 2012?

There are several means available to protect VMs with Windows Server 2012. One of the new Hyper-V 3.0 features is Replica, which replicates VMs between remote Hyper-V platforms or clusters using ordinary WAN links such as the Internet. The feature is system and storage agnostic, so administrators can protect VMs in a secondary data center or a distant DR site.

Replica is an asynchronous function, so workloads do not need to wait for replication to complete. There is no disruption to the workloads, which is particularly handy when replicating over significant geographic distances where latency may be problematic or over low-bandwidth WAN connections where the actual data movement may take longer than expected.

As with other snapshot-type replication tools, Replica can also be used to copy production VMs over to test and development systems. The replicated data can then be used without jeopardizing production data.

IT administrators should take another look at updates to Windows Server's virtual machine snapshots feature. Previous versions of the feature forced administrators to take a workload offline when recovering storage space from deleted snapshots (.avhd files). With Windows Server 2012, the VM can remain running while related snapshot files are deleted. This behavior is far less disruptive to the workloads and users.

Systems administrators face constant challenges in managing virtualization and improving the performance of virtualized workloads. The next iteration of Hyper-V included with Windows Server 2012 addresses the principal concerns in VM storage demands, VM management automation and VM data protection.

This was first published in January 2013

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