Q: What are the key new capabilities in Windows Server 10?

A: The technical preview exposes a number of key new capabilities in Windows Server, which are by no means the final capabilities but just the ones we know about right now. They include the following (this isn't an exhaustive list, just the things I think are the most interesting):

  • Rolling Hyper-V cluster upgrade. This is a huge feature that customers have been asking for. It allows a Windows Server 2012 R2 cluster to be upgraded one node at a time in a mixed-mode configuration. Once all nodes have been upgraded, a PowerShell cmdlet is run (Update-ClusterFunctionalLevel), which then turns on the Windows Server 10 native clustering functionality. Previously, clustered nodes had to be removed from the cluster, a new cluster created, and resources migrated. This rolling upgrade will allow organizations to adopt new server releases faster and with less pain.
  • New Hyper-V virtual machine configuration format. The new VMCX format is a binary format file, which means it can't be directly edited. Existing virtual machines can be upgraded to the new format using the Update-VmConfigurationVersion cmdlet, which is a one-way migration operation. Note that virtual machines in a cluster can't be upgraded to the new format until the cluster functional level is Windows Server 10.
  • Ability to create production checkpoints. A checkpoint is a point-in-time capture of a virtual machine's storage and device/memory state, which can then be reverted to at some later point in time. However, this was focused around test/development use because the virtual machine is unaware of the checkpoint capture and therefore the state could be inconsistent. The new production checkpoints enables the VSS infrastructure within the Windows virtual machine to be called. (In Linux, the file system buffers are flushed out, which makes the OS in an application-consistent state and therefore usable in production environments). Note that this still doesn't eliminate the need for regular backups. You can use the old-style checkpoints if you prefer, as well as configure the old-style checkpoints to be used if the production checkpoint can't be created (e.g., if the backup integration service isn't available).
  • Hyper-V Manager improvements. Leverages WS-MAN for communication to Hyper-V hosts, enabling other types of authentication and the use of alternative credentials. Can also manage down-level Hyper-V servers (down to Windows Server 2012)
  • Hot add of network adapters and memory to Generation 2 virtual machines for Windows and Linux. This allows memory to be changed even when dynamic memory isn't being used.
  • Hyper-V Integration Services in guest virtual machines will be updated via Windows Update.
  • Storage QoS on Scale-Out File Servers, which enables cluster-wide QoS to ensure that storage performance needs are met.
  • Windows Defender is now included in Windows Server; no graphical interface is installed by default, but one can be added.
  • OpenGL 4.4 and OpenCL 1.1 are now supported with RemoteFX, in addition to the ability to dedicate larger amounts of VRAM to virtual machines.
  • Storage Replica, which provides synchronous mirroring of data between nodes in a cluster or between standalone servers. Asynchronous storage replication is also available, with the risk of possible data loss.
  • Improvements to DNS client for multi-homed machines.
  • Support for GRE tunneling, which enables connectivity between virtual networks and external networks.
  • New Network Controller role, which exposes information about the network infrastructure (such as virtual and physical networks, in addition to various services and IP topology) to other management applications, such as SCVMM and SCOM.
  • Numerous web application proxy improvements focused around application publishing.
  • PowerShell 5.0 with numerous new modules.