The way I do it is as follows. I use 4 SATA 300 Gbyte drives in a raid 0 raid array. Extremely fast indeed. But this drives are backed up daily on alternate drive 0 array's, one array is using two 500 Mbyte sata drives, the second array uses 500 Mbyte IDE drives. I use Acronics True image server software. On switching off the computer, it makes an incremental backup to one array. The next day the backup goes to the other array, and so on. I boot from the 4 sata drives, only takes about 15 seconds before I can use the machine. Depending where bad sectors are they can indeed destroy raid one arrays. Never use JBCD arrays. The possible failure rate is simply to big as your files are unpredictable spread over two or more drives. Also there is practically no speed increase at all. I hope that this covers your questions.
Regards
Jurgen