PC magazine has a very good article on back up strategy and devices. The whole article is here Your Backup Battle Plan
An effective data backup strategy means knowing what needs to be backed up, including regulations such as the Health Insurance Portability and Accountability Act (HIPPA), which has specific backup requirements. You should also determine whether data should be backed up or archived. Most businesses do both. Backups are copies of active data for short-term use and are frequently overwritten with updated versions. The three types of backup are full (which backs up all files regardless of whether they have changed), differential (which backs up all files modified since the last full backup), and incremental (which backs up only files that have changed since the last backup of any kind). Archives, on the other hand, contain static data, such as inactive document files and old e-mails.
The article suggests a move away from tape back up which has been the standard to disc back up using removable hard drives or off site back up using the Internet.