What why how
We need information on how current RAID controllers (and software RAID solutions?) perform in varioius scenarios. As of now (Februar 2007) there is no such project to my knowledge. Current acquirement practices usually involve just buying whatever brand the person in charge fancys; hardly any benchmarking is done and results are often less than satisfactory.
Education about setting up RAID controllers might also be helpful. How many people can tell you by heart what the difference between Write-Back and Write-Through is and how this affects application performance and data safety.
Types of benchmarks
I'd opt for blockdevice-level benchmarks and application-level Benchmarks. FS (bonnie++, iozone, etc.) benchmarks are too muddy for raw controller performance due to the many layers between the Filesystem and the blockdevice to give useful numbers.
Block Device Benchmarks
Research sane benchmark sets for various databases.
I'd use MySQL with MyISAM tuned for "speed" as candidate for the relational-textfile style of database user and PostgreSQL configured for reliability (default) for real Database workload.
Use a webserver (lighttpd, apache2 mpm_worker) configured for maximum throughput to serve a given fileset. The client must be able to replay request patterns and report statistics.