There's no longer a cap on the number of migrations you can perform simultaneously, apart from the limitations of your hardware. Windows Server 8 also lets you queue migrations in a single operation that moves VMs one at a time. And you can specify priority VMs to avoid failures when a cluster becomes oversubscribed. If a cluster is loaded with more VMs than it can handle in a failover scenario, Windows Server 8 will shut down low-priority VMs to allow high-priority VMs to run.
Advanced virtual networking. If you've chafed against the lack of promiscuous mode in the Hyper-V virtual switch or pined for the virtual networking capabilities in VMware, you'll be happy to know that Microsoft has dived in with both feet in Windows Server 8. Microsoft seems to have matched the VMware vSwitch feature for feature -- port ACLs, private VLANs, per-vNIC bandwidth reservations, QoS, metering, OpenFlow support, VN-Tag support, network introspection -- all without requiring expensive network devices. The switch will support third-party extensions for inspecting, filtering, modifying, sampling, and inserting packets, with management of the extensions integrated into Hyper-V.
Hyper-V Replica. One of the best features of virtualization is easy disaster recovery, but this isn't as simple as it could be in Windows Server 2008 R2 Hyper-V. The clumsy process for setting up virtual machine replication in R2 gives way to a simple wizard in Windows Server 8. After you choose the virtual disks to replicate and the location for the replicas, you have the option of syncing immediately, scheduling the sync, or writing the replica to a local disk -- if you want to bring up the replica on a big USB drive and ship it to the other end for the initial load. The result is an asynchronous, application-consistent snapshot that's no more than five minutes behind the primary VM. You can even specify the IP settings for the failover environment within the replica, and failback is supported.
SMB for server apps. Windows Server 8 gives a big boost to small businesses and branch offices by extending support for Hyper-V virtual hard disks and SQL Server database files to SMB2 file shares. Translation: You can run your virtual machines and SQL database from a commodity file server, no special storage system required. To protect your Hyper-V and SQL workloads, you can create "continuously available" SMB file server clusters that provide transparent failover. That's high availability made very cheap and very easy.
VDI for the rest of us. Virtual Desktop Infrastructure will change the world -- but not until it becomes a whole lot simpler to do. Setting up and managing virtual desktops on Windows Server 2008 R2 pales miserably to Citrix XenApp/XenDesktop, for example, and implementing Citrix is no walk in the park. Windows Server 8 takes a big step forward toward reducing the complexity and costs of a VDI deployment.
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