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File synchronization

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File synchronization (or 'syncing') in computing is the process of making sure that files in two or more locations are updated through certain rules.[citation needed]

In one-way synchronization, also called mirroring, updates files are copied only from a 'source' location to a 'target' location, or locations, but no files are copied back to the source location. In two-way sync, updated files are copied in both directions, usually with the purpose of keeping the two locations identical to each other. The term synchronization is used in this article to mean exclusively two-way file synchronization.[citation needed]

File synchronization is commonly used for home backups on external hard drives or updating for transport on USB flash drives. The automatic process prevents copying already identical files and thus can save considerable time from a manual copy, also being faster and less error prone.[1] However this suffers from the limitation that the synchronized files have to physically fit in the portable drive. Synchronization software that only keeps a list of files and the changed files circumvents this problem (e.g. the "snapshot" feature in Beyond Compare or the "package" feature in Synchronize It!). It is particularly useful for mobile workers, or others that work on multiple computers. It is possible to synchronize multiple locations by synchronizing them a pair at a time.

Common features

  • Encryption for security, particularly when synchronizing across the Internet.
  • Compressing any data sent across a network, this requires a server.
  • Conflict detection where a file has been modified on both sources, as opposed to where it has only been modified on one. No conflict detection 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 vectors.
  • 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. Although most synchronizing programs can be used in this way, providing specific support for this can reduce the amount of data stored on the device.
  • The ability to preview any changes before they are made.
  • The ability to view differences in individual files.

Software

This is a list of notable file synchronization software. See also built-in file synchronization functionality in Windows XP [1].

Open source

A comparison of free and open source file synchronization software.

Name Protocol Programming Language Platforms License Version Conflict detection
CleanSync file system C# Windows GPL 1.0 [03-Apr-2010] Yes
Create Synchronicity file system VB.Net Windows GPL 3.0 [25-Feb-2010] No
DirSync Pro file system Java Windows, Linux, Mac OS X GPL 1.21 [17-Feb-2010] No
DoubleSnap for synchronizing digital photos C# Windows GPL 1.0 [03-Apr-2010] Yes
F-A-S-T (File Archiving and Sync Tool) file system C# Windows GPL 1.0 [03-Apr-2010] Yes
FreeFileSync file system C++ Windows, Linux GPL 3.6 [31-Mar-2010] Yes (centralized database)
GameAnywhere For synchronizing game settings C# Windows GPL 1.0 [03-Apr-2010] Yes
iFolder file system C#/Mono Windows, Linux, Mac OS X GPL 3.8 [25-Nov-2009] Yes
JFileSync file system Java Any Java 5.0 or higher runtine GPL 2.2 [20-July-2007] Yes
NETS (Nothing Else To Sync) file system C# Windows GPL 1.0 [03-Apr-2010] Yes
NSync file system C# Windows GPL 1.0 [03-Apr-2010] Yes
OneSync file system C# Windows GPL 1.0 [03-Apr-2010] Yes
Replicator file system Visual Basic Windows 3.6.8 [28-Nov-2009] No
rsync file system C in the Unix/Linux shell Windows, Linux, OS X, other Unix GPL 3.07 [31-Dec-2009] No
SubSync file system C#/Mono Windows, Linux GPL 1.0 [03-Apr-2010] Yes
SyncButler file system C# Windows GPL 1.0 [03-Apr-2010] Yes
SyncDesk file system C# Windows GPL 1.0 [03-Apr-2010] Yes
Syncless file system C# Windows GPL 1.0 [03-Apr-2010] Yes
SyncSharp file system C# Windows GPL 1.0 [03-Apr-2010] Yes
SyncWizard file system C# Windows GPL 1.0 [03-Apr-2010] Yes
Synkron file system C++ Windows, Linux, OS X GPL 1.6.1 [16-Oct-2009] Yes
Tzync file system C# Windows GPL 1.0 [03-Apr-2010] Yes
Unison similar to rsync; uses SSH (or file system) as transport OCaml Windows, Linux, OS X, other Unix GPL 2.32.52 [29-Jun-2009] Yes (centralized database)

Commercial

A comparison of proprietary software released as commercial.

Name Windows Mac Linux Other OS Open source Online backup service Freeware version Paid version Conflict detection File Locking Open File Support previous file versions / revision control
Distributed Storage Yes No Yes No No via other providers No Yes Yes Yes Yes
Allway Sync Yes No No No No via other providers Yes Yes Yes
BackupAssist Yes No No No No via Rsync No Yes No Yes
Dmailer Sync Yes No No No No Yes Yes Yes
Dropbox Yes Yes Yes Yes: iPhone No Yes Yes Yes Yes Yes
Easy Computer Sync Yes No No No No Yes Yes Yes
GoodSync Yes Yes No No No Yes Yes Yes Yes Yes Yes Yes
Handy Backup Yes No No No No No Yes No
PowerFolder Yes Yes Yes No Partial Yes Yes Yes Yes Yes[2]
Robocopy Yes No No No No No Yes Yes No
SpiderOak Yes Yes Yes No Partial Yes Yes Yes Yes[3]
SugarSync Yes Yes No Yes: Android, iPhone, BlackBerry, Windows Mobile No Yes Yes Yes Yes[4]
SuperFlexible Yes Yes No No No Yes No Yes Yes No Yes Yes
SyncBack Yes No No No No No Yes Yes Yes Yes
Synchronize It! Yes No No No No No No Yes No
Syncplicity Yes No No No No Yes Yes Yes Yes
TeamDrive Yes Yes Yes No No Yes Yes Yes Yes Yes
Ubuntu One No No Yes No Partial Yes Yes Yes
Wuala Yes Yes Yes No Partial Yes Yes Yes
ZumoDrive Yes Yes Yes Yes: iPhone, Android, Palm webOS No Yes Yes Yes Yes Yes
PEER Collaboration Package Yes Yes Yes No Yes Yes Yes Yes Yes
RepliWeb Deployment Yes No Yes Yes No No No Yes Yes (partial) Yes

Freeware

This is a list of proprietary software released as freeware or gratis.

Name OS Vendor online cloud storage remote desktop previous file versions / revision control Comments
Microsoft ActiveSync Windows Microsoft No No ? syncs mobile devices
Windows Mobile Device Center Windows Microsoft No No ? syncs mobile devices. Successor to Microsoft ActiveSync
Gbridge Windows Gbridge LLC ? Yes ? Sync folders, Remote desktop, Live web browsing, etc.
Microsoft Sync Framework Windows Microsoft ? No ? syncs files, data and services. A framework, not a tool.
Microsoft SyncToy Windows Microsoft No No ? Sync local folders.
Microsoft Live Mesh Windows, Windows Mobile, OSX Microsoft Yes Yes No (Recycle Bin only?) Sync folders, Remote desktop, cloud storage. (Beta software, it's likely to be merged into Windows Live Sync soon(cited).)
Windows Live Sync Windows, OSX Microsoft Yes No No (Recycle Bin only?) Sync folders, cloud storage. (Previously Microsoft FolderShare) 20,000 file limit.
broolz Windows, OSX (& Linux in development) broolz Yes No Yes Sync folders, user defined cloud storage, collaborate and backup. Some features disabled for beta phase.

See also

References

  • Kerner, Sean (2008-02-13). "Get In Sync with File Syncing Software". Tom's Guide. Retrieved 2009-07-01.
  • Kerner, Sean (2008-02-27). "Syncing Software Redux: More Options". Tom's Guide. Retrieved 2009-07-01.
  • "A List of File Synchronization Tools". Retrieved 2010-04-03.
  1. ^ A. Tridgell (February 1999). "Efficient algorithms for sorting and synchronization" (PDF). PhD thesis. The Australian National University. {{cite journal}}: Cite journal requires |journal= (help)
  2. ^ ""PowerFolder File Sync Archive"". PowerFolder. Retrieved 2010-01-23.
  3. ^ Susie Ochs (2009-06-11). ""Online Storage Battle: Which Cloud Back-Up Service Reigns Supreme?"". MacLife. Retrieved 2009-11-04.
  4. ^ ""See How SugarSync Stacks up to the Competition"". SugarSync (formerly called SharpCast). Retrieved 2010-01-13.
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