The main intent of RAID 1 is to avoid computer and data downtime if a hard drive fails. You can still lose your data because of human error, viruses, theft, fire, flood, and RAID controller failure. If your data is important, I advise maintaining separate backups, preferably offsite. Those backups can be on tapes, removable hard drives, or CD/DVD.
For many small organizations, the best combination of cost and ease of use is often two or more external hard drives (Firewire, USB, or SATA). Keep one drive attached, making automated backups, and keep a second drive elsewhere. Swap out the drives periodically, based upon how much data you can afford to lose if disaster strikes.
Just be sure to test your backups periodically. People often make the mistake of not testing their backups, finding out too late that the backups can't be read, or that they aren't backing up all their data. If you can afford the drive space, I recommend simply making FULL system backups, making impossible to miss backing up something important.
Yes, you can make a SATA RAID 1 array. I use them all the time. But get a good backup system first. After that, if you have extra time and money and want to minimize the chances of having a computer down because of drive failure, THEN install a RAID 1 array.