Windows Server 2008: preview, part 2

Alan Stevens ZDNet.co.uk

Published: 16 Jul 2007

In the first part of this preview we said that Windows Server 2008 was more or less complete and ready for launch. That, it seems, was a little premature, as a number of important announcements have been made since then that affect both the content and release schedule of the product. First the release date, which won’t be the end of 2007 as everyone had anticipated. The official launch has now been put back to 27 February 2008, although the product may slip out to enterprise customers before that — the February date is more about being able to stage a glitzy launch event than finalising the code.

As well as being a lot later than expected, the new release schedule also has implications for the much-talked-about Windows Server Virtualization (WSV) option — which we'll examine in more detail shortly. Microsoft had already announced that this wouldn’t be released along with the main server software, promising that it would be launched sometime within the following 180 days. As such, it may now appear as late as July/August 2008.

Another change is an about-face on deploying the IIS 7.0 Web server on the new cut-down Server Core implementation of Windows Server 2008. Originally this wasn’t included as one of the possible roles but 'due to customer demand', it is now a supported configuration. However, there are a few provisos such as a lack of graphical management tools. There’s also no .NET Framework for Server Core, which means that ASP.NET won’t be available either — although standard ASP will work, and you will get the new FastCGI support and PHP facilities provided as part of IIS 7.0.

Virtual enhancements
The most keenly anticipated feature of Windows Server 2008 is the virtualisation technology codenamed Viridian, now officially called Windows Server Virtualization (WSV). First, it’s important to understand how WSV will differ from the current Virtual Server 2005 product, which will continue to be developed alongside the Windows Server 2008 solution.

The principal difference is that, like many virtualisation products, Virtual Server 2005 runs as an application on top of a host operating system, sharing out the physical resources on that host among one or more virtual machines (VMs) running guest operating systems. This arrangement means that the virtualisation software can only communicate with the underlying hardware indirectly, through the host operating system. Also, for the sake of compatibility, it emulates standard hardware interfaces for things like storage and network access, further impacting performance.

By contrast, WSV is a 'hypervisor' implementation whereby the virtualisation software runs directly on the underlying hardware, without the need for a host operating system. In theory, this results in enhanced performance and security compared to hosted alternatives such as both Virtual Server 2005 and market leader VMWare’s rival VMWare Server product.

WSV is not the first hypervisor solution, though. VMWare also leads the market here with ESX Server (now part of its VMware Infrastructure platform), with Xen increasingly popular in the open source space. Moreover, it’s not quite the case that you don’t need a host OS with WSV, as Microsoft has opted for what it calls a 'micro-kernelised' implementation, with the drivers needed to communicate with the underlying hardware stripped out of the hypervisor to minimise its size. So, although the hypervisor doesn’t run as a Windows application, WSV does need a primary partition running Windows Server 2008 to work, although this can be Server Core rather than the full graphical operating system.

Another big difference compared to Virtual Server 2005 is the replacement of standard hardware interfaces and emulators with new drivers that are optimised to use the underlying hypervisor technology more effectively. For these to work, however, the guest virtual machines need to run so-called 'enlightened' operating systems containing the necessary code to work with this new technology.

That restricts compatibility, although Windows Server 2008 will itself come with these 'enlightened' drivers, allowing it to be run as a guest on WSV, as does Windows Vista. Microsoft will also provide enlightened extensions for Windows XP and Windows Server 2003 and is partnering with XenSource to develop enlightenments to enable Linux to be employed as a guest OS.

Windows Server Virtualisation (WSV) employs a 'micro-kernelised' hypervisor with a primary partition running Windows Server 2008 and 'enlightened' guests configured to use its optimised I/O drivers.

Like Virtual Server 2005, Windows Server Virtualisation will be available free of charge — although because it’s dependent on Windows Server 2008, you do have to spend money to deploy it. Also, WSV can only be used on 64-bit server hardware equipped with the latest Intel or AMD processors with hardware virtualisation support. Although the latest R2 SP1 release of Virtual Server 2005 can also exploit these processor extensions, WSV is totally dependent on them.

On the plus side, WSV will be a lot more scalable than Virtual Server 2005. For example, whereas Virtual Server 2005 is limited to 32-bit virtual machines with a single virtual CPU, WSV can run either 32-bit or 64-bit guests with up to eight virtual processors/cores per VM. Each guest will also get up to 32GB of memory (Virtual Server 2005 VMs can be configured with just 3.6GB) and perhaps more as Microsoft has yet to determine what the final limit will be.

WSV wasn’t in the Beta 3 of Windows Server 2008 released in May, but at that time Microsoft announced that it would be available to run on host servers with up to 64 processors/cores. Since then, however, that number has been cut back to 16. The company has also back-pedalled on plans to support dynamic allocation of VM resources and live migration of active VMs from one host to another — key features in VMWare’s market-leading alternative.

These options will now be made available in a later release — possibly the first service pack, although that’s far from definite and no dates have been specified. It’s also worth noting that the live migration feature will be dependent on the enhanced high-availability clustering services provided by Windows Server 2008 (see below). There’s one other caveat: basic management tools are included with WSV, but if you want to manage multiple implementations you’ll need to wait until System Center Virtual Machine Manager is available. Beta 2 of the software can be downloaded now, but the release version isn’t due until the end of 2007 and could possibly be delayed given the issues getting WSV itself off the blocks.

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Windows Server 2008: preview, part 1

Preview Windows Server 2008, formerly codenamed Longhorn Server, is due in the second half of this year. In the first instalment of a two-part preview, we take a look at some of the key functionality in Beta 3. [25 May 2007]