LSI supports a number of controllers under ClearOS specifically by name. Additionally, many of their devices will simply 'just work'. Look for compatibility with ClearOS, RHEL, or CentOS when selecting a components from LSI.
search?q=clearos%2C%20hardware%2C%203rdparty%2C%20LSI%2C%20MegaRAID%2C%20maintainer_dloper&btnI=lucky