Digital photography has forced professionals to rethink archiving of work. Physical negatives have transformed into digital files, which are only as stable as the media on which they are stored.
Hard disks are extremely delicate pieces of technology: a magnetic storage disc read by a mechanism that under normal circumstances never physically comes in contact with the platter. Problems arise when conditions are not normal; if the reading mechanism touches the platter… well, kiss the data goodbye. Computer hard disks are more reliable than they were a decade ago, but disk failure is still a fact of life.
So, it's not a matter of if a hard disk will fail; it's a matter of when a disk will fail. Armed with this knowledge, it's imperative that photographers implement a solid backup scheme for digital images. This article is going to cover one way of protecting data – RAID 1 storage.

Western Digital 1TB External Hard Drive