File synchronization
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File synchronization (or syncing) in computing is the process of ensuring that
computer file A computer file is a computer resource for recording data in a computer storage device, primarily identified by its file name. Just as words can be written to paper, so can data be written to a computer file. Files can be shared with and transfe ...
s in two or more locations are updated via certain rules. In ''one-way file synchronization'', also called mirroring, updated files are copied from a source location to one or more target locations, but no files are copied back to the source location. In ''two-way file synchronization'', updated files are copied in both directions, usually with the purpose of keeping the two locations identical to each other. In this article, the term synchronization refers exclusively to two-way file synchronization.
File File or filing may refer to: Mechanical tools and processes * File (tool), a tool used to ''remove'' fine amounts of material from a workpiece **Filing (metalworking), a material removal process in manufacturing ** Nail file, a tool used to gent ...
synchronization is commonly used for home backups on external hard drives or updating for transport on
USB flash drives A USB flash drive (also called a thumb drive) is a data storage device that includes flash memory with an integrated USB interface. It is typically removable, rewritable and much smaller than an optical disc. Most weigh less than . Since first ...
.
BitTorrent Sync Resilio Sync (formerly BitTorrent Sync) by Resilio, Inc. is a proprietary peer-to-peer file synchronization tool available for Windows, Mac, Linux, Android, iOS, Windows Phone, Amazon Kindle Fire and BSD. It can sync files between devices on a ...
,
Dropbox Dropbox is a file hosting service operated by the American company Dropbox, Inc., headquartered in San Francisco, California, U.S. that offers cloud storage, file synchronization, personal cloud, and Client (computing), client software. Dropb ...
and SKYSITE are prominent products. Some
backup software Backup software are computer programs used to perform a backup; they create supplementary exact copies of files, databases or entire computers. These programs may later use the supplementary copies to restore the original contents in the event of ...
also support real-time file sync. The automatic process prevents copying already identical files and thus can be faster and save much time versus a manual copy, and is less error prone. However this suffers from the limit that the synchronized files must physically fit in the portable storage device. Synchronization software that only keeps a list of files and the changed files eliminates this problem (e.g. the "snapshot" feature in
Beyond Compare Beyond Compare is a proprietary data comparison utility. Aside from comparing files, the program is capable of doing side-by-side comparison of directories, FTP and SFTP directories, Dropbox directories, Amazon S3 directories, and archives. It i ...
or the "package" feature in Synchronize It!). It is especially useful for mobile workers, or others that work on multiple computers. It is possible to synchronize multiple locations by synchronizing them one pair at a time. The
Unison In music, unison is two or more musical parts that sound either the same pitch or pitches separated by intervals of one or more octaves, usually at the same time. ''Rhythmic unison'' is another term for homorhythm. Definition Unison or per ...
Manual describes how to do this: : If you need to do this, the most reliable way to set things up is to organize the machines into a "star topology," with one machine designated as the "hub" and the rest as "spokes," and with each spoke machine synchronizing only with the hub. The big advantage of the star topology is that it eliminates the possibility of confusing "spurious conflicts" arising from the fact that a separate archive is maintained by
Unison In music, unison is two or more musical parts that sound either the same pitch or pitches separated by intervals of one or more octaves, usually at the same time. ''Rhythmic unison'' is another term for homorhythm. Definition Unison or per ...
for every pair of hosts that it synchronizes.


Common features

Common features of file synchronization systems include: *
Encryption In cryptography, encryption is the process of encoding information. This process converts the original representation of the information, known as plaintext, into an alternative form known as ciphertext. Ideally, only authorized parties can decip ...
for
security Security is protection from, or resilience against, potential harm (or other unwanted coercive change) caused by others, by restraining the freedom of others to act. Beneficiaries (technically referents) of security may be of persons and social ...
, especially when synchronizing across the
Internet The Internet (or internet) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a '' network of networks'' that consists of private, pub ...
. * Compressing any data sent across a network. * ''Conflict detection'' where a file has been modified on both sources, as opposed to where it has only been modified on one. Undetected conflicts can lead to overwriting copies of the file with the most recent version, causing data loss. For conflict detection, the synchronization software needs to keep a database of the synchronized files. Distributed conflict detection can be achieved by
version vector A version vector is a mechanism for tracking changes to data in a distributed system, where multiple agents might update the data at different times. The version vector allows the participants to determine if one update preceded another (happened-b ...
s. * ''Open Files Support'' ensures data integrity when copying data or application files that are in-use or database files that are exclusively locked. * Specific support for using an intermediate storage device, such as a removable flash disc, to synchronize two machines. Most synchronizing programs can be used in this way, but providing specific support for this can reduce the amount of data stored on a device. * The ability to preview any changes before they are made. * The ability to view differences in individual files. * Backup between operating systems and transfer between network computers. * Ability to edit or use files on multiple computers or operating systems.


Possible security concerns

Consumer-grade file synchronization solutions are popular, however for business use, they create a concern of allowing corporate information to sprawl to unmanaged devices and cloud services which are uncontrolled by the organization.


See also

*
Comparison of file synchronization software Glossary Free and open-source Freeware This is a comparison of the freeware (proprietary software release free of charge) file synchronization software. Commercial This is a comparison of commercial software in the fie ...
*
Comparison of online backup services This is a comparison of online backup services. Online backup is a special kind of online storage service; however, various products that are designed for file storage may not have features or characteristics that others designed for backup have ...
*
Data synchronization Data synchronization is the process of establishing consistency between source and target data stores, and the continuous harmonization of the data over time. It is fundamental to a wide variety of applications, including file synchronization and m ...
*
Data comparison In computing, file comparison is the calculation and display of the differences and similarities between data objects, typically text files such as source code. The methods, implementations, and results are typically called a diff, after the Un ...
* Mirror (computing) *
Backup software Backup software are computer programs used to perform a backup; they create supplementary exact copies of files, databases or entire computers. These programs may later use the supplementary copies to restore the original contents in the event of ...
*
List of backup software This is a list of notable backup software that performs data backups. Archivers, transfer protocols, and version control systems are often used for backups but only software focused on backup is listed here. See Comparison of backup software f ...
*
Remote backup service A remote, online, or managed backup service, sometimes marketed as cloud backup or backup-as-a-service, is a service that provides users with a system for the backup, storage, and recovery of computer files. Online backup providers are companies ...
*
Shared file access In computing, a shared resource, or network share, is a computer resource made available from one host to other hosts on a computer network. It is a device or piece of information on a computer that can be remotely accessed from another compu ...


References

{{DEFAULTSORT:File synchronization Storage software Utility software types