I have been working on a proof of concept testing an Active/Active/Passive Exchange 2007 cluster running on Windows 2008 SP2.  We have been working to connect a Netapp 3170 SAN to the cluster.  We encountered some challenges connecting the SAN to the servers.  I have summarized the lessons learned below:

• Challenge #1:  Had problem getting the MPIO stack recognized by the Netapp SnapDrive software.  We had loaded the Netapp DSM and Snapdrive software but wasn't able to connect to the Microsoft MPIO stack.  After hours of troubleshooting, we determined that there is a 3rd Netapp software component that is required:  Host Utilities.  The order of install should be:  Host Utilities, DSM, and Snapdrive.
• Challenge #2:  To build the Exchange 2007 cluster, we loaded the Windows 2008 clustering components.  Our next step was to configure and present the LUNs to the servers, Netapp does this work from the Exchange server using their Snapdrive software [Note:  This is different from other SAN vendors where the storage is carved and presented to the server from the back-end].  When we attempted to run the Snapdrive software to do this carving, we got some RPC errors (RPC server is not responding).  The Netapp software would work fine when we disabled the Windows clustering services, but encountered errors when we enabled the clustering services.  Unfortunately, if you disable the Windows clustering services and run the Netapp software, Netapp configures the drives in dedicated mode (versus a shared mode needed for clustering) so we couldn't configure the LUNs with the clustering service stopped.  After some troubleshooting, we determined that the Windows 2008 firewall was preventing the Netapp software from communicating with the storage.  We enabled the Windows clustering services and disabled the Windows 2008 firewall (must be done in the 3 locations: domain profile, private prfoile, and public profile).  After doing these steps, we were able to connect and configure the LUNs.