If you have tried setting up LVM on top of a LVM-enabled software-RAID partition during a standard Suse installation you may have hit a brick wall where the installer tells you that there are no available LVM partitions. This is a bug in the installer, it looks as if the LVM setup tool only checks physical partitions for LVM labels and ignores software-RAID partitions that have LVM labels.
Steve Wray has pointed out that you can get this functionality to work by creating a small physical partition and giving it an LVM label. The LVM setup tool will see this partition and allow the configuration to continue quite happily with the software-RAID partitions available for use. I have not tested this but I think it is worth giving a spin as the data integrity of RAID-1 coupled with the flexibility of LVM is a compelling combination (though performance maybe an issue).
Note: From a bit of Googling it appears that this limitation is not apparent in Suse Linux Enterprise Server by the looks of this IBM documentation.