A blog on this same subject has just been posted to You Had Me At EHLO... and there are a few points that I'll add here which I didn't include in my original blog 'Windows 2008 or Windows 2003?'. (...and I apologise for lifting these points directly from Scott's article. There didn't seem much chance of me improving on his eloquence...)
So here are some more benefits of Windows 2008 that Exchange will benefit from:
"Faster log file shipping: Cluster Continuous Replication and Standby Continuous Replication are two forms of log shipping that use the Server Message Block (SMB) protocol to copy log files from a source storage group to a passive or target storage group. Windows Server 2008 includes SMB version 2, which provides a significant increase (around 30-40%) in SMB-based file copying throughput and performance.
Reduced downtime for hardware maintenance Windows Server 2008 enables a variety of core hardware components to be added, removed or replaced without requiring system downtime. These processes are often referred to as "hot add", "hot remove", "hot replace" because the system remains active and continues providing service and data access while the hardware maintenance is occurring. Dynamic hardware partitioning in Windows Server 2008 includes support for hot add and replacement of processors and memory, as well as hot pluggable PCI Express cards. Of course, support for this is available only with the appropriate hardware. If you're not sure if your hardware is capable of running Windows Server 2008, you can download the Microsoft Assessment and Planning tool to securely inventory your existing servers and generate a migration report for Windows Server 2008.
Greater scalability for Client Access servers that provide Outlook Anywhere services: Windows Server 2008 includes a Next Generation TCP/IP stack that removes the RPC Proxy Service TCP connection limits imposed by Windows Server 2003 and earlier versions of Windows. Specifically, the RPC Proxy Service, the Windows component that enables RPC over HTTP, now supports per-IP address connection-limits. Whereas the RPC Proxy Service in Windows Server 2003 supports a maximum of 65,535 connections, regardless of the number of IP addresses assigned to the server, the RPC Proxy Service in Windows Server 2008 supports a maximum of 65,535 connections per IP address.
Easier deployment: Windows Server 2008 includes Exchange 2007 installation dependencies, such as Microsoft Management Console (MMC) 3.0, Windows PowerShell, and .NET Framework 2.0. As a result, you don't need to separately download these prerequisites in order to deploy Exchange 2007 SP1 on Windows Server 2008. Instead, you can quickly install them from the new Server Manager MMC console in Windows Server 2008, or install them from the command-line version of Server Manager.
Support for IPv6: Windows Server 2008 includes support for IPv6, and Exchange 2007 SP1 supports IPv6 on Windows Server 2008 when used in tandem with IPv4. For more information, see IPv6 Support in Exchange 2007 SP1."
So I never made the connection between SMB-based file copying and faster transaction log shipping... Seems obvious now but didn't realise that this is the mechanism that is used and a 30-40% improvement in throughput and performance is significant, as Scott says. ..and I have certainly come near the connection limit for CAS and mailbox roles when designing for very large deployments of Outlook Anywhere.
Another consideration when choosing between Windows 2008 and 2003 is going to be backups...
"Unlike previous versions of Windows, Windows Server 2008 does not include a backup utility that supports the Exchange ESE streaming backup APIs. The Windows 2008 backup application, Windows Server Backup, cannot be used to take backups of Exchange.
Exchange still includes the ESE streaming backup APIs, but the absence of an Exchange-aware backup application in Windows may come as a surprise to many. Another change we made that may also affect you is the removal of remote streaming backup support on Windows 2008.
This leaves you with two choices for taking Exchange-aware online backups when running Exchange 2007 SP1 on Windows 2008:
- Move to a Volume Shadow Copy Service (VSS)-based backup application. You can use Microsoft System Center Data Protection Manager (DPM) 2007 or a third-party backup application that supports Exchange-aware VSS-based backups of Exchange 2007 SP1 on Windows Server 2008. Windows Server Backup in Windows 2008 is a VSS-based backup application, but it does not include a VSS requestor for Exchange, which is a necessary component in order to use VSS to take an Exchange-aware backup.
- Use a Third-Party application that supports ESE streaming backups using a local backup agent on the Exchange server. Because the ESE streaming APIs remain in Exchange 2007, you can still use them to backup Exchange. But to do that, you must use a third-party backup application that runs a local agent on the Exchange server so that the streaming backup is made locally, and not remotely. You cannot take remote streaming backups of Exchange 2007 SP1 on Windows 2008 with or without a third-party product. Any streaming backups that are performed must be performed locally on the Exchange server."
I think the choice for most therefore is going to be to wait until their current backup provider releases a version of the product that will backup Exchange 2007 running on Windows 2008 (either streaming or VSS) and I have to admit I am not sure where the big players are on this front; or switch to DPM. There is more and more information out there about DPM including a number of good case studies which should make the product less of a risk than a lot of companies still believe it to be. Of course the other choice is not to backup altogether but that's another story altogether...