Data at rest

Data at rest in information technology means inactive data that is stored physically in any digital form (e.g. databases, data warehouses, spreadsheets, archives, tapes, off-site backups, mobile devices etc.).

Data at rest is used as a complement to the terms data in use and data in transit which together define the three states of digital data (see Figure 1).

There is some disagreement as to the boundary between data at rest and data in use. Data at rest generally refers to data stored in persistent storage (disk, tape) while data in use generally refers to data being processed by a computer central processing unit (CPU) or in random access memory (RAM, also referred to as main memory or simply memory). Definitions include:

"...all data in computer storage while excluding data that is traversing a network or temporarily residing in computer memory to be read or updated."

"...all data in storage but excludes any data that frequently traverses the network or that which resides in temporary memory. Data at rest includes but is not limited to archived data, data which is not accessed or changed frequently, files stored on hard drives, USB thumb drives, files stored on backup tape and disks, and also files stored off-site or on a storage area network (SAN)."

Data in use has also been taken to mean “active data” in the context of being in a database or being manipulated by an application. For example, some enterprise encryption gateway solutions for the cloud claim to encrypt data at rest, data in transit and data in use.

While it is generally accepted that archive data (i.e. which never changes), regardless of its storage medium, is data at rest and active data subject to constant or frequent change is data in use, “inactive data” could be taken to mean data which may change, but infrequently. The imprecise nature of terms such as “constant” and “frequent” means that some stored data cannot be comprehensively defined as either data at rest or in use. These definitions could be taken to assume that Data at Rest is a superset of data in use; however, data in use, subject to frequent change, has distinct processing requirements from data at rest, whether completely static or subject to occasional change.

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