The availability and protection of data can be usefully illustrated in terms of a continuum:
At the beginning of the continuum sits high availability. This requirement is usually satisfied by redundancy and fault tolerant designs. The goal here is continuous availability and the avoidance of downtime by the use of redundant components and services.
Further along the continuum lie the data recovery approaches in order of decreasing timeliness. These solutions typically include a form of point-in-time snapshots for fast recovery, followed by synchronous and asynchronous replication. Finally, backup to tape or a virtual tape library sits at the end of the continuum, providing insurance against large-scale data loss, natural disasters, and other catastrophic events.