Provide more details. The SAN device almost always provides the RAID service. It does not make sense to provide drives from a SAN when all of these devices are capable of doing the RAID faster than the OS (software raid). What you probably want to do is define the RAID groups on the storage device and then present devices from the SAN from those groups accordingly.
Who manages your storage? Do you have a storage admin and what is the storage device you are using?