Thinking about using a setup for smaller offices that uses the
server's internal Raid5 setup in a mirror to an external SATA/Raid.

This off course isn't a problem itself, but worth checking is;
1. Speed can only be as good as the slowest part of the setup,
in this case,, I'd say that the internal SCSI Raid5 is quicker, so
the inclusion of the SATA/Raid will lower the max-performance

This is no problems,
But,, is there any "dangers" with this speed difference ?
or should Netware handle this mirroring anyway ?