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.

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synchronization is commonly used for home backups on external hard drives or updating for transport on

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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 ...

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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

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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

for every pair of hosts that it synchronizes.

Common features

Common features of file synchronization systems include: *

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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.

References

{{DEFAULTSORT:File synchronization Storage software Utility software types

Common features

Possible security concerns

See also

References