Windows Server 2008, popularly known by its code name Longhorn, is a significant release for Microsoft and represents the result of a very long development cycle.

We've all heard about many features that made it into the final release. But what you may have missed is the actual impact that Longhorn's final version will have on your organization.

[ Read Tom Yager's review of Windows Server 2008 in InfoWorld's Test Center ]

Some of the enhancements work pretty much as expected: restartable ActiveDirectory Domain Services (AD DS) and several integrity-related NTFS enhancements are two examples. Other Longhorn changes can take quite a bit of planning to deliver what you'd want, plus may require you to buy new hardware to take advantage of them: Server Core, RODCs (read-only domain controllers), failover clustering, multi-path I/O, and Next Generation TCP/IP.

We've also all been hearing for years now about the features slated for this release that got cut, such as WinFS, and ones that customers had hoped Microsoft would include, such as SysInternals. Their omissions too have consequences for your organization.

Here's InfoWorld's guide to what you need to know about these key changes in Longhorn.

Restartable ActiveDirectory Domain Services
In previous versions of Windows Server, if ActiveDirectory installation becomes corrupt and an authoritative restore is necessary, you need to bring down the server and boot it in a special mode to do that restoration. The server and all of its services are completely down during this time.

Longhorn changes that scenario with Restartable ActiveDirectory Domain Services. Just turn off AD DS, and when you restore ActiveDirectory or do anything else with the database, the rest of the server's services are still online. That means Windows Server 2008 can still handle DNS, DHCP, WINS, and all other requests. The one thing it can't do while AD DS is off is authenticate users.

The only caveat on using Restartable AD DS involves human error: It's possible to forget to turn the service back on.

Although you should rarely need to use Restartable AD DS, it's nice to have for those times you do have to restore a large server, which can take 30 minutes or so to boot.

NTFS enhancements
Microsoft has made me very happy with its enhancements to NTFS. In Longhorn, NTFS is no longer just a file system. Instead, it's an active part of the server and its integrity.

One of the changes, transactional NTFS, is just phenomenal. It lets you define transactions for server-level operations, so you can, for example, set up a transaction that copies files to a directory, creates a registry entry, and registers a DLL. Because these changes are handled as a single transaction, Longhorn ensures that they all complete or that the entire operation rolls back. That way, you won't have an orphaned registry entry because the files didn't copy over properly.

You can put anything into a transaction and enjoy the full atomicity, consistency, isolation and durability (ACID) properties that database people have enjoyed for years. The really nifty part about this is that you can also coordinate these server-level OS transactions with SQL Server or MSMQ transactions. For example, you could load data, FTP some files, and run an SSIS package all inside a transaction and not have to worry about picking up the pieces should one step fail.