Once, Strata sourced a RAID system for a client without explicitly checking how backups would be done. She was shocked and dismayed to find that the vendor claimed that backups were unnecessary! The vendor did plan- eventually-to support a tape device for the system, but that would not be for at least a year.
Adding a high-speed interface card to the box-to keep backups off the main computing network-was an acceptable workaround for the client. When purchasing a storage system, ask about backup and restore options.