Microsoft's [[ArtId:992677851|Windows Server 2008|new] will present a number of challenges, including application compatibility concerns, to users looking to migrate given its palette of new components, APIs, and feature upgrades, experts say.

Some issues will be familiar to those who rolled out Vista, including user-account control, which restricts user privileges, and the Windows Firewall, which is turned on by default. Vista also has an ongoing issue with application compatibility that is not cleared up in the pending release of Vista Service Pack 1. Other issues unique to Windows Server 2008, such as new, clustering APIs, will require application testing and some recoding of applications, according to Microsoft.

The server also will present issues for in-place upgrades and upgrades to servers running Exchange 2007.

Experts say Windows Server 2008, which has been under development for five years, provides many improvements over the current platform; but getting there from currently installed software will require some perseverance and result in methodical rollouts. "The comparison should not be to Windows 2003, it should be to Windows 2000," says Al Gillen, an IDC analyst. "2003 was an improved version of 2000, but [Windows Server 2008] is not an improved version of Windows Server 2003 R2. [Windows Server 2008] has enough new stuff in it that it will cause people to go through a whole evaluation and scenario planning activity. It is disruptive in a lot of respects and will impact application compatibility." Gillen says he anticipates a substantial impact on older applications, although he said he does not yet have a sense how extensive or invasive the impact might be.

One area that Microsoft has already highlighted is clustering, where it has rewritten the MSClus APIs that shipped with Windows Server 2003. Microsoft says the new APIs provide better features, scalability and management, but it acknowledges that applications using the old APIs will break or provide incorrect results if they are run on Windows Server 2008.

In addition, changes in session isolation can break applications, because Windows Server 2008 now divides system services and applications into separate sessions where before they ran in one session. Microsoft says the new architecture improves security but drivers -- such as print drivers loaded by the spooler service -- and applications -- such as those creating globally named objects -- will fall victim to session isolation.

In addition, Windows Server 2008 will present a learning curve for some users who have yet to get their hands dirty with the beta. That could be a sizeable chunk of users. According to a recent survey by Walker Information and CDW, 72 per cent of 772 IT pros surveyed said they "know little about" Windows Server 2008, which is expected to be released February 27. Of the 20 per cent who said they had some familiarity with the server, 86 per cent said they had yet to start testing or evaluating the software.

Those users will be presented with such new features as Server Core and Server Roles, which are designed to make setup and configuration easier, but will be part of the learning curve. "These things present new deployment scenarios that users have to think about," Gillen says. He also says users need to think long-range about moving to virtualization and how 64-bit platforms factor into that.

Microsoft plans to release its Hyper-V virtualization technology at least 180 days after Windows Server 2008 ships.

Small-to-midsize companies also may want to test Microsoft's upgraded Windows Small Business Server (SBS) 2008, formerly called Cougar, and Windows Essential Business Server (EBS) 2008 for Midsize Companies, formerly called Centro, which are bundles of Microsoft infrastructure software designed for smaller companies. SBS is for users with a maximum of 50 desktops, while EBS tops out at 250. Both are built on top of Windows Server 2008 and are expected to ship in the fall.

Microsoft also is integrating online services for such features as security and document sharing.