ABSTRACT
Snapshots have become an almost ubiquitous feature within data protection services, regardless of whether they occur at the operating system, hypervisor, or storage layer. There are a variety of snapshot techniques that can be used in data protection, and in this chapter, the authors review several of the more common techniques and their applicability. The snapshot is presented as being a separate filesystem to the filesystem it is protecting, effectively seen as an independent entity even though the actual data is shared between the source and the snapshot. Copy on First Access (CoFA) is a snapshot process typically associated with generating clones of data, typically at the volume/LUN level. These initially look quite similar to a CoFW snapshot, in that the snapshot copy starts as a set of pointers back to the original content that was snapshot.
