Where Windows 8 is an operating system built for the tablet, Windows Server 8 is an operating system built for the cloud. Not the Windows Azure public cloud; rather, it's built for "private clouds": on-premises, virtualized deployments with tens or hundreds of virtual machines.
This kind of large scale administration requires a new approach to system management. That approach centers around PowerShell and Server Manager, the new Metro-style management console. Server Manager provides a convenient GUI, but behind the scenes, PowerShell commands are constructed and executed. The commands can also be copied, edited, and executed directly in PowerShell. This should sound familiar to many Windows administrators, as Exchange already uses this style of management, with the GUI being a mere layer over PowerShell.
The same mechanism is used to administer multiple machines simultaneously; it makes remote PowerShell calls to multiple machines, allowing actions to be performed on them in parallel. To enable this, PowerShell has been expanded with more than 2,000 new commands.
Going hand in hand with this new style of administration is a new approach to the GUI. Windows Server 2008 has Server Core mode, a way of running windows with the GUI removed. This hasn't received much uptake, however—quite a few applications, though server-oriented, just don't work without the GUI for one reason or another. Switching between Server Core and the standard operating system requires reinstallation.
Windows Server 8 will have three modes. Microsoft has added to the two existing modes—the traditional GUI mode, with the full GUI stack and shell, and Server Core, that offers only a command-line—a third that's somewhere in the middle. It doesn't include the full shell, so there's no Explorer or Internet Explorer, but it does include Server Manager and MMC. Moreover, the graphical shell will be an installable component that can be added or removed at any time.
The idea of all this is not that GUIs shouldn't be used for administration—this isn't a regression to a UNIX-style command-line УМber alles approach—but that the administration should be remote. Servers themselves should have the barest minimum software installed in order to reduce their attack surface area.
Fundamental to the "private cloud" concept is powerful virtualization. Windows Server 8 will include Hyper-V 3, which is more scalable and more fully-featured than its predecessors. Host machines can have up to 160 logical processors and 2TB RAM. Virtual machines can have up to 32 cores and 512GB RAM, and with the new VHDX file format, virtual disks can be up to 16TB big (up from the current 2TB). The number of machines supported on a host will be limited only by resource availability with no fixed ratios.
To go with these uprated capabilities are new features. Offloaded Data Transfer (ODX) allows more efficient use of SANs. Virtualization is now NUMA aware, to ensure that Virtual Machines prefer local memory. Virtual machines will support up to four fibre channel HBAs. The virtual network switch will allow NIC teaming, for greater networked performance, and will enable virtual machines to be isolated with private VLANs.
Hyper-V three includes a number of new fault tolerance features. Windows Hardware Error Architecture support will allow Hyper-V to better tolerate memory errors; if an error is detected, Hyper-V will suspend all VMs, determine which one suffered the memory error, reboot it, and unsuspend the other machines. This prevents an ECC memory error from taking down the entire set of virtual machines. Asynchronous replicas, demonstrated earlier in the year, will enable virtual machines to be continuously copied to a disaster recovery site, for example. Hyper-V 3 will support simultaneous live machine migration and live storage migration. This will allow host servers to easily be patched and rebooted without any guest service interruption.
To make resource usage of virtualized servers even more efficient, Windows Server 8 will include deduplication technology. Memory deduplication allows identical pages in memory to be shared. In normal desktop usage, this doesn't happen too often—most of the information stored in RAM is different, as it all belongs to different applications. But that's no longer the case when running multiple virtual machines; each virtual machine will have its own copy of the operating system, applications, and so on, and these will tend to be identical across the virtual machines. Sharing that memory allows the host to reclaim hundreds or thousands of megabytes of memory.
Memory isn't the only thing that's typically duplicated when virtualizing systems: disk images routinely contain exact duplicates of gigabytes of operating system data. Windows Server 8 includes storage deduplication. A background task will find identical blocks on disk, and allow it to be shared between multiple files.
Deduplication isn't anything new. VMware has had both memory and storage deduplication from some years (along with a number of patents to go with it). But that doesn't make it any less welcome—Microsoft demonstrations of the technology reduced the disk footprint of a VDI server by some 96 percent. Microsoft's approach is also different from that of a virtualization system like VMware, insofar as it's not restricted to virtualization workloads. File servers too can benefit from the technology. The result should be both more robust and more effective than Microsoft's long-abandoned Single Instance Store feature, that would allow exact duplicate files to be shared.
Storage hasn't just gained deduplication. Storage Pools allow creation of virtual drives that span physical disks. The pools are then carved into separate volumes. The Storage Pool system allows software RAID-like features, as well as support for overprovisioning.
Windows Server 8 is every bit as big a release Windows 8. It's big in a different way—evolution rather than revolution—but the improvements are extensive and their consequences far-reaching. VMware, in particular, will feel challenged: Hyper-V is becoming a lot more capable, and when that's combined with Windows Datacenter's already compelling licensing model, more and more Windows shops will turn to Microsoft's virtualization solution. There's work still to do—the operating system still isn't feature complete—but it should prove to be a substantial upgrade and welcome improvement for Windows administrators.