Backup strategy which requires:
- 3 copies of data (1 primary, 2 backups)
- 2 media types (or devices)
- 1 copy left off site
Originally, the idea behind using two types of storage media was twofold. One, it protects you from one of those forms of media becoming obsolete in the face of new storage technology and your data becoming unreadable with new storage technology. And two, it’s wise to keep your backup copy on a separate device so that a hardware failure doesn’t take out both local copies.
(About cloud providers) The cloud service provider is responsible for maintaining the physical storage devices and keeping your data accessible at all times. So, if you use a cloud backup service, you only need to worry about keeping your data on two devices, not two separate kinds of media.