This is the default partitioning scheme that we encountered via a support call with someone having problems with their SBS 2008 install:
If the factory OEM install was used, or if the Dell preparation utility disk was used and the utility was allowed to install the Dell Utility Partition, the above is what we would end up with.
In our case, we always flatten the RAID arrays and start fresh without the utility partitioning schemes and set up our default partitioning for SBS 2008 (SBS 2008 Setup Checklist post).
The catch with the setup above is that the SBS 2008 Backup will fail out of the box. That FAT32 partition will break it.
Using the Diskpart command we can convert that partition to NTFS and at least get the SBS 2008 Backup to run successfully.
In the end, the above leads to a messy partitioning scheme along with the possibility of causing problems in the event of a failed RAID array.
We prefer to keep things simple. :)
Microsoft Small Business Specialists
Co-Author: SBS 2008 Blueprint Book